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Even and odd functions

Learning goals

  • Tests functions algebraically for even or odd symmetry.
  • Recognizes y-axis and origin symmetry from graphs.
  • Uses symmetry to infer values or graph behavior.

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Even and odd functions 1
Classify \(f(x)=x^4+3\) as even, odd, or neither.

Hints

- Compare \(f(-x)\) with \(f(x)\). - An even power is unchanged when \(x\) is replaced by \(-x\).

Solution

1. Substitute \(-x\): \(f(-x)=(-x)^4+3=x^4+3\). 2. Since \(f(-x)=f(x)\), the function is even.

Answer

Even.
Even and odd functions 2
The table gives every value of a function \(h\) on its domain \(\{-3,-1,0,1,3\}\). <table> <tr><th>\(x\)</th><th>\(-3\)</th><th>\(-1\)</th><th>\(0\)</th><th>\(1\)</th><th>\(3\)</th></tr> <tr><td>\(h(x)\)</td><td>\(4\)</td><td>\(2\)</td><td>\(1\)</td><td>\(2\)</td><td>\(4\)</td></tr> </table> Is \(h\) even, odd, or neither?

Hints

- Compare the outputs at opposite inputs. - Check whether the domain contains both \(x\) and \(-x\) for each nonzero input.

Solution

1. The domain is symmetric about \(0\). 2. The paired inputs have matching outputs: \(h(-1)=h(1)=2\) and \(h(-3)=h(3)=4\). 3. Therefore, \(h(-x)=h(x)\) for every input in the domain, so \(h\) is even.

Answer

Even.
Even and odd functions 3
The function \(f\) is even and \(f(4)=7\). Find \(f(-4)\).

Hints

- Recall what an even function does at opposite inputs. - Compare the input \(-4\) with the given input.

Solution

1. For an even function, \(f(-x)=f(x)\). 2. Therefore, \(f(-4)=f(4)=7\).

Answer

\(f(-4)=7\)
Even and odd functions 4
The function \(h\) is odd and \(h(-2)=5\). Find \(h(2)\).

Hints

- Think about how outputs change when the inputs of an odd function have opposite signs. - Apply that relationship to the value already given.

Solution

1. For an odd function, \(h(-x)=-h(x)\). 2. The output at \(2\) is the opposite of the output at \(-2\), so \(h(2)=-5\).

Answer

\(h(2)=-5\)
Even and odd functions 5
Use the table to decide whether \(f\) is even, odd, or neither. Explain using its values. <table><tr><th>\(x\)</th><th>\(-2\)</th><th>\(-1\)</th><th>\(0\)</th><th>\(1\)</th><th>\(2\)</th></tr><tr><th>\(f(x)\)</th><td>\(3\)</td><td>\(1\)</td><td>\(2\)</td><td>\(4\)</td><td>\(3\)</td></tr></table>

Hints

- An even function gives equal outputs at opposite inputs. - What must an odd function's output at \(0\) be? - You only need one counterexample to rule out each type.

Solution

1. The outputs at \(-1\) and \(1\) are \(1\) and \(4\), so they are not equal. The function is not even. 2. Since \(f(0)=2\), the function cannot be odd; an odd function defined at \(0\) must have \(f(0)=0\). 3. Therefore, it is neither even nor odd.

Answer

Neither; \(f(-1)\ne f(1)\), and \(f(0)\ne0\).
Even and odd functions 6
The function \(f(x)=\sqrt{x}\) has domain \(x\ge0\). Is \(f\) even, odd, or neither? Give a reason.

Hints

- Before checking outputs, look at which inputs are allowed. - Does every allowed positive input have a matching negative input?

Solution

1. A function must have both \(x\) and \(-x\) in its domain to be even or odd. 2. The input \(1\) is allowed, but \(-1\) is not, so the domain is not symmetric about \(0\). 3. Therefore, the function is neither even nor odd.

Answer

Neither; its domain contains \(1\) but not \(-1\).
Even and odd functions 7
Is the graphed function even, odd, or neither? State the symmetry you used.
Figure for problem 560698

Hints

- Compare points whose x-coordinates are opposites. - Are their y-coordinates equal or opposite?

Solution

1. The line passes through the origin, and each point \((x,y)\) has a matching point \((-x,-y)\). 2. This is origin symmetry, so the function is odd.

Answer

Odd; the graph has symmetry about the origin.
Even and odd functions 8
Which function has a graph that is symmetric about the origin? a) \(y = x(4 - x^2)\) b) \(y = x(4 - x)\) c) \(y = (4 - x)(4 + x)\) d) \(y = x(4 - x)^2\)

Hints

- Recall the equation that defines an odd function. - Expand each expression and examine the powers of \(x\). - You can also compare the function values at \(x = 1\) and \(x = -1\).

Solution

1. A graph is symmetric about the origin when its function is odd, so \(f(-x) = -f(x)\). 2. For a), \(f(x) = x(4 - x^2) = 4x - x^3\). Both terms have odd powers, so \(f(-x) = -f(x)\). 3. For b), \(f(x) = 4x - x^2\), which contains both odd and even powers. 4. For c), \(f(x) = 16 - x^2\), which is even and is symmetric about the y-axis. 5. For d), \(f(x) = 16x - 8x^2 + x^3\), which contains both odd and even powers.

Answer

a) \(y = x(4 - x^2)\)
Even and odd functions 9
Which function has a graph that is symmetric about the y-axis? a) \(f(x)=x^3+1\) b) \(f(x)=(x^3-1)^2\) c) \(f(x)=(x^3+1)^2\) d) \(f(x)=(x^3-1)(x^3+1)\)

Hints

- Use the condition \(f(-x)=f(x)\). - Consider how even and odd powers change when \(x\) is replaced by \(-x\). - Expanding or using a special-product identity may reveal the powers more clearly.

Solution

1. A graph is symmetric about the y-axis when \(f(-x)=f(x)\). 2. For choice d), use the difference of squares: \(f(x)=x^6-1\). 3. Then \(f(-x)=(-x)^6-1=x^6-1=f(x)\), so choice d) is even. 4. The other choices contain a nonzero odd-power term after expansion, so they do not satisfy \(f(-x)=f(x)\).

Answer

d) \(f(x)=(x^3-1)(x^3+1)\)
Even and odd functions 10
Let \(A(x)=\frac{12}{4-x^2}\). a) Which real inputs are excluded from its domain? b) Find \(A(1)\) and \(A(-1)\). c) Show that \(A(-x)=A(x)\) for every allowed input. Is \(A\) an even function?

Hints

- Which numbers make the denominator zero? - Compare what happens when you square a positive number and its opposite. - An even function must allow opposite inputs and have matching outputs for them.

Solution

1. The denominator is zero when \(4-x^2=0\), so exclude \(x=-2\) and \(x=2\). 2. Substitution gives \(A(1)=\frac{12}{3}=4\) and \(A(-1)=\frac{12}{3}=4\). 3. For each allowed \(x\), \(A(-x)=\frac{12}{4-(-x)^2}=\frac{12}{4-x^2}=A(x)\). 4. The domain is unchanged when \(x\) is replaced by \(-x\), so \(A\) is even.

Answer

a) \(x=-2\) and \(x=2\). b) \(A(1)=A(-1)=4\). c) \(A(-x)=A(x)\) on the domain; yes, \(A\) is even.
Even and odd functions 11
The point \(Q(2,-16)\) lies on each of the two candidate power functions \(p(x)=-x^4\) and \(q(x)=-2x^3\). The actual graph also passes through \(R(-2,16)\). a) Prove from the definitions that \(p\) is even and \(q\) is odd. b) Without substituting \(-2\) into either formula, determine which candidate passes through \(R\). Justify your choice using the symmetry of even and odd functions.

Hints

- Apply \(f(-x)\) to each candidate before using either given point. - Compare how y-axis symmetry and origin symmetry transform the point \((2,-16)\). - Do not recompute the formulas at \(x=-2\); use the established parity instead.

Solution

1. For \(p\), \(p(-x)=-(-x)^4=-x^4=p(x)\), so \(p\) is even. 2. For \(q\), \(q(-x)=-2(-x)^3=2x^3=-q(x)\), so \(q\) is odd. 3. An even function sends opposite inputs to the same output, so because \(p(2)=-16\), symmetry would require \(p(-2)=-16\), not \(16\). 4. An odd function sends opposite inputs to opposite outputs, so because \(q(2)=-16\), symmetry requires \(q(-2)=16\). Therefore, \(q\) is the candidate that passes through \(R\).

Answer

a) \(p\) is even and \(q\) is odd. b) \(q(x)=-2x^3\), because odd symmetry sends \((2,-16)\) to \((-2,16)\).
Even and odd functions 12
For each equation, suppose \(r\ne0\) is a real solution. Without calculating \(r\), use whether the corresponding power function is even or odd to determine what must be true about \(-r\). a) \(r^6=10\): does \(-r\) solve the same equation or the sign-changed equation \(x^6=-10\)? b) \(r^3=-8\): does \(-r\) solve the same equation or the sign-changed equation \(x^3=8\)? c) \(r^4=5\): does \(-r\) solve the same equation or the sign-changed equation \(x^4=-5\)? d) \(r^5=7\): does \(-r\) solve the same equation or the sign-changed equation \(x^5=-7\)?

Hints

- Classify each power function as even or odd before considering \(-r\). - For an even function, opposite inputs have the same output. - For an odd function, opposite inputs have opposite outputs.

Solution

1. The function \(x^6\) is even, so \((-r)^6=r^6\). Therefore, if \(r^6=10\), then \((-r)^6=10\); \(-r\) solves the same equation. 2. The function \(x^3\) is odd, so \((-r)^3=-r^3\). Since \(r^3=-8\), \((-r)^3=8\); \(-r\) solves the sign-changed equation. 3. The function \(x^4\) is even, so \((-r)^4=r^4=5\); \(-r\) solves the same equation. 4. The function \(x^5\) is odd, so \((-r)^5=-r^5=-7\); \(-r\) solves the sign-changed equation.

Answer

a) Same equation: \((-r)^6=10\) b) Sign-changed equation: \((-r)^3=8\) c) Same equation: \((-r)^4=5\) d) Sign-changed equation: \((-r)^5=-7\)
Even and odd functions 13
Let \(p_n(x)=x^n\), where \(n\) is a positive integer, and let \(r\ne0\). a) Prove that when \(n\) is even, \(p_n(-r)=p_n(r)\). Explain what this guarantees about the two inputs \(r\) and \(-r\) whenever one of them produces a nonzero output \(c\). b) Prove that when \(n\) is odd, \(p_n(-r)=-p_n(r)\). Explain how a point \((r, c)\) on the graph determines the point with opposite input. c) State the corresponding graph symmetry in each case.

Hints

- The only algebraic difference between the two cases is the sign of \((-r)^n\). - Connect the resulting equality to the definitions of even and odd functions. - Translate the input-output relationship into a statement about reflected points on the graph.

Solution

1. If \(n\) is even, then \((-r)^n=r^n\), so \(p_n(-r)=p_n(r)\). Thus, whenever \(p_n(r)=c\ne0\), the opposite input \(-r\) produces the same output \(c\). 2. If \(n\) is odd, then \((-r)^n=-r^n\), so \(p_n(-r)=-p_n(r)\). Thus, if \((r, c)\) lies on the graph, then \((-r, -c)\) also lies on the graph. 3. Even-power graphs are symmetric about the y-axis. Odd-power graphs are symmetric about the origin.

Answer

a) For even \(n\), \(p_n(-r)=p_n(r)\); opposite inputs give the same output. b) For odd \(n\), \(p_n(-r)=-p_n(r)\); \((r, c)\) pairs with \((-r, -c)\). c) Even \(n\): y-axis symmetry. Odd \(n\): origin symmetry.
Even and odd functions 14
Rania claims: “If \(r\) is a solution of \(x^n=c\), where \(c\ne0\), then \(-r\) is always a solution of \(x^n=-c\).” Determine whether the claim is true for even exponents and for odd exponents. Justify each case using the definitions of even and odd functions, not by solving particular equations.

Hints

- Rewrite the claim as a statement comparing \(f(r)\) and \(f(-r)\). - Use the defining equation for an even function in one case and an odd function in the other. - Do not calculate any specific roots; the statement is about all inputs.

Solution

1. If \(n\) is even, then \(f(x)=x^n\) is even, so \(f(-r)=f(r)=c\). Therefore, \(-r\) solves \(x^n=c\), not \(x^n=-c\) when \(c\ne0\). The claim is false for even exponents. 2. If \(n\) is odd, then \(f(x)=x^n\) is odd, so \(f(-r)=-f(r)=-c\). Therefore, \(-r\) does solve \(x^n=-c\). The claim is true for odd exponents.

Answer

Even \(n\): false, because \((-r)^n=r^n=c\). Odd \(n\): true, because \((-r)^n=-r^n=-c\).
Even and odd functions 15
The graph of \(f(x)=kx^n\), where \(k\ne0\) and \(n\) is a positive integer, passes through \(P(-2,4)\). Do not solve for \(k\). a) If \(n\) is even, determine the point on the graph with x-coordinate \(2\). Justify your answer by classifying \(f\) as even or odd. b) If \(n\) is odd, determine the point on the graph with x-coordinate \(2\). Justify your answer by classifying \(f\) as even or odd. c) Explain why multiplying \(x^n\) by the nonzero constant \(k\) does not change whether the function is even or odd.

Hints

- Determine how \((-x)^n\) behaves for even and odd \(n\). - Apply that sign behavior inside the full expression \(kx^n\). - Use the appropriate graph symmetry to infer the point at the opposite input.

Solution

1. If \(n\) is even, then \((-x)^n=x^n\). Therefore, \(f(-x)=k(-x)^n=kx^n=f(x)\), so \(f\) is even. Since \((-2, 4)\) is on the graph, \((2, 4)\) is also on the graph. 2. If \(n\) is odd, then \((-x)^n=-x^n\). Therefore, \(f(-x)=k(-x)^n=-kx^n=-f(x)\), so \(f\) is odd. Since \((-2, 4)\) is on the graph, \((2, -4)\) is also on the graph. 3. The constant multiplier \(k\) appears in both \(f(x)\) and \(f(-x)\). It does not change whether replacing \(x\) by \(-x\) preserves the output or changes its sign, so it does not change the parity determined by \(n\).

Answer

a) \((2, 4)\); for even \(n\), \(f\) is even. b) \((2, -4)\); for odd \(n\), \(f\) is odd. c) Multiplication by nonzero \(k\) preserves the relation \(f(-x)=f(x)\) for even \(n\) and \(f(-x)=-f(x)\) for odd \(n\).
Even and odd functions 16
Determine algebraically whether each function is even, odd, or neither. a) \(f(x)=\frac{x^2-9}{x^2+1}\) b) \(g(x)=\frac{1}{2}x^3-2x\) c) \(h(x)=x^2(x-3)\)

Hints

- Replace \(x\) with \(-x\) in each rule. - Compare the result with the original function and its negative. - Expand the product in part c) if needed.

Solution

1. For \(f\), \(f(-x)=\frac{(-x)^2-9}{(-x)^2+1}=\frac{x^2-9}{x^2+1}=f(x)\). Therefore, \(f\) is even. 2. For \(g\), \(g(-x)=\frac{1}{2}(-x)^3-2(-x)=-\frac{1}{2}x^3+2x=-g(x)\). Therefore, \(g\) is odd. 3. Expand \(h(x)=x^3-3x^2\). Then \(h(-x)=-x^3-3x^2\), which is neither \(h(x)\) nor \(-h(x)\). Therefore, \(h\) is neither even nor odd.

Answer

a) Even; symmetric about the y-axis b) Odd; symmetric about the origin c) Neither even nor odd
Even and odd functions 17
For the polynomial family \(f_a(x)=x^4+(a^2-1)x^3+3x^2\), determine whether exactly one or more than one real value of \(a\) makes \(f_a\) even.

Hints

- Identify the term that prevents the polynomial from being even. - Set its coefficient equal to \(0\). - Solve the resulting quadratic equation completely.

Solution

1. An even polynomial can contain only even powers with nonzero coefficients. 2. Therefore, the coefficient of \(x^3\) must equal \(0\): \(a^2-1=0\). 3. Factoring gives \((a-1)(a+1)=0\), so \(a=1\) or \(a=-1\). 4. Thus, more than one real parameter value works.

Answer

There are two values: \(a=-1\) and \(a=1\).
Even and odd functions 18
Let \(f(x)=3x^4-5x^2+7\). 1) Use the powers in the rule to identify the graph's symmetry. 2) Maia wants to change only the constant term \(7\) so that the resulting function is odd. Determine whether this is possible and explain.

Hints

- Classify each exponent as even or odd. - Remember that a nonzero constant is an \(x^0\) term. - Decide whether changing one coefficient affects the other terms.

Solution

1. Every nonzero term has an even exponent, including the constant term with exponent \(0\). Therefore, \(f(-x)=f(x)\), so \(f\) is even. 2. An odd polynomial can contain only odd-power terms with nonzero coefficients. Changing the constant term can remove the \(x^0\) term by setting it to \(0\), but the terms \(3x^4\) and \(-5x^2\) remain. 3. Therefore, changing only the constant term cannot make the function odd.

Answer

1) The function is even and its graph is symmetric about the y-axis. 2) It is impossible. The even-power terms \(3x^4\) and \(-5x^2\) remain regardless of the constant term.
Even and odd functions 19
Let \(h(x)=x^5-4x^3+kx\), where \(k\in\mathbb{R}\). 1) Show algebraically that \(h\) is odd for every value of \(k\). 2) Explain why \(g(x)=h(x)+3\) is not odd.

Hints

- Replace \(x\) with \(-x\) in every term. - Compare the shifted function at \(-x\) with its negative. - Interpret adding \(3\) as a vertical translation.

Solution

1. Substitute \(-x\): \(h(-x)=(-x)^5-4(-x)^3+k(-x)=-x^5+4x^3-kx=-h(x)\). Thus, \(h\) is odd for every real \(k\). 2. For \(g\), \(g(-x)=-h(x)+3\), while \(-g(x)=-h(x)-3\). Since these expressions are not equal, \(g\) is not odd. 3. Geometrically, adding \(3\) shifts the graph upward, moving its center of symmetry from \((0, 0)\) to \((0, 3)\).

Answer

1) \(h(-x)=-h(x)\) for every \(k\), so \(h\) is odd. 2) \(g(-x)=-h(x)+3\ne-h(x)-3=-g(x)\), so \(g\) is not odd.
Even and odd functions 20
Let \(f(x)=\frac{x^2+3x}{x^2+4}\). Determine algebraically whether its graph is symmetric about the y-axis, symmetric about the origin, or neither.

Hints

- Compute \(f(-x)\) carefully. - Compare it first with \(f(x)\), then with \(-f(x)\). - A symmetry identity must hold for every value in the domain.

Solution

1. Substitute \(-x\): \(f(-x)=\frac{x^2-3x}{x^2+4}\). 2. This is not equal to \(f(x)=\frac{x^2+3x}{x^2+4}\) for all \(x\), so \(f\) is not even. 3. Also, \(-f(x)=\frac{-x^2-3x}{x^2+4}\), which is not equal to \(f(-x)\) for all \(x\). Therefore, \(f\) is not odd. 4. The graph has neither symmetry.

Answer

The graph is neither symmetric about the y-axis nor symmetric about the origin.
Even and odd functions 21
Consider \(g(x)=\frac{x^4-1}{(x-2)(x+5)}\). Use the domain to explain why the graph can be neither symmetric about the y-axis nor symmetric about the origin.

Hints

- Find the values that make the denominator \(0\). - Check whether every excluded value has its opposite excluded as well. - Both standard symmetries require a domain that is symmetric about \(0\).

Solution

1. The denominator is \(0\) at \(x=2\) and \(x=-5\), so the domain is \(\mathbb{R}\setminus\{-5, 2\}\). 2. Either y-axis symmetry or origin symmetry requires the domain to be symmetric about \(0\): whenever \(x\) is in the domain, \(-x\) must also be in the domain. 3. Here, \(5\) is in the domain but \(-5\) is not. Similarly, \(-2\) is in the domain but \(2\) is not. 4. Therefore, the domain fails a necessary condition for both symmetries.

Answer

The domain is \(\mathbb{R}\setminus\{-5, 2\}\), which is not symmetric about \(0\). Therefore, the graph has neither y-axis symmetry nor origin symmetry.
Even and odd functions 22
Let \(T_1(x)=3x^2+10\) and \(T_2(x)=2x^3\). a) Evaluate both functions at \(x=4\) and \(x=-4\). b) For a general real number \(x\), simplify \(T_1(-x)\) and \(T_2(-x)\). c) A function is even when \(f(-x)=f(x)\) for every input in its domain and odd when \(f(-x)=-f(x)\). Classify \(T_1\) and \(T_2\) as even or odd and justify each classification using part b.

Hints

- Numerical values at opposite inputs can suggest a pattern, but they do not prove a function is even or odd. - Substitute \(-x\) for the input and simplify before comparing with the original function. - Compare the simplified result with \(f(x)\) and with \(-f(x)\).

Solution

1. a) \(T_1(4)=3\cdot4^2+10=58\) and \(T_1(-4)=3\cdot(-4)^2+10=58\). Also, \(T_2(4)=2\cdot4^3=128\) and \(T_2(-4)=2\cdot(-4)^3=-128\). 2. b) \(T_1(-x)=3(-x)^2+10=3x^2+10=T_1(x)\). 3. \(T_2(-x)=2(-x)^3=-2x^3=-T_2(x)\). 4. c) Because \(T_1(-x)=T_1(x)\) for every real \(x\), \(T_1\) is even. Because \(T_2(-x)=-T_2(x)\) for every real \(x\), \(T_2\) is odd.

Answer

a) \(T_1(4)=T_1(-4)=58\); \(T_2(4)=128\) and \(T_2(-4)=-128\) b) \(T_1(-x)=T_1(x)\); \(T_2(-x)=-T_2(x)\) c) \(T_1\) is even and \(T_2\) is odd, by the defining relationships in part b.
Even and odd functions 23
The polynomial function \(f\) is defined by \(f(x) = 2x^4 + (a + 3)x^3 - 5x^2\). Find the value of \(a \in \mathbb{R}\) that makes the graph symmetric about the y-axis. Verify your answer using the condition \(f(-x) = f(x)\).

Hints

- Recall which powers can appear in an even polynomial function. - Determine which coefficient must equal zero. - Substitute \(-x\) for \(x\) to verify the even-function condition.

Solution

1. A polynomial is even only when the coefficients of all odd-power terms are zero. 2. The coefficient of \(x^3\) must be zero, so \(a + 3 = 0\). Therefore, \(a = -3\). 3. Substituting \(a = -3\) gives \(f(x) = 2x^4 - 5x^2\). 4. Then \(f(-x) = 2(-x)^4 - 5(-x)^2 = 2x^4 - 5x^2 = f(x)\). Therefore, the graph is symmetric about the y-axis.

Answer

\(a = -3\)
Even and odd functions 24
Consider \(g(x) = \frac{1}{2}x^5 - 4x^3 + x\). 1. Determine algebraically whether the graph of \(g\) is symmetric about the origin. 2. Decide whether \(h(x) = g(x) + 5\) is also symmetric about the origin. Justify your answer using the symmetry condition.

Hints

- Recall the equation that defines an odd function. - Track the sign of each term after substituting \(-x\) for \(x\). - Determine how adding the constant \(5\) affects the equation \(h(-x) = -h(x)\).

Solution

1. Substitute \(-x\): \(g(-x) = \frac{1}{2}(-x)^5 - 4(-x)^3 + (-x) = -\frac{1}{2}x^5 + 4x^3 - x\). 2. This expression equals \(-g(x)\), so \(g(-x) = -g(x)\). Therefore, \(g\) is odd and its graph is symmetric about the origin. 3. For \(h(x) = g(x) + 5\), \(h(-x) = g(-x) + 5 = -g(x) + 5\). 4. However, \(-h(x) = -g(x) - 5\). Since \(h(-x) \ne -h(x)\), \(h\) is not odd and its graph is not symmetric about the origin.

Answer

1. Yes. \(g(-x) = -g(x)\), so \(g\) is symmetric about the origin. 2. No. \(h(-x) = -g(x) + 5\), while \(-h(x) = -g(x) - 5\).
Even and odd functions 25
For each condition, give two different choices of exponents \(n\) and \(m\) from \(\{1, 2, 3, 4, 5, 6\}\) and a constant \(c \in \mathbb{R}\) so that \(f(x) = x^n + 5x^m + c\) satisfies the condition. a) The graph of \(f\) is symmetric about the y-axis. b) The graph of \(f\) is symmetric about the origin.

Hints

- Determine whether each symmetry condition requires even powers or odd powers. - Treat the constant \(c\) as the term \(cx^0\). - Decide whether a vertical shift is compatible with symmetry about the origin.

Solution

1. For symmetry about the y-axis, \(f\) must be even. Therefore, \(n\) and \(m\) must both be even. The constant \(c\) may be any real number. Two examples are \((n, m, c) = (2, 4, 3)\) and \((6, 2, 0)\). 2. For symmetry about the origin, \(f\) must be odd. Therefore, \(n\) and \(m\) must both be odd, and the constant term must be zero. Two examples are \((n, m, c) = (1, 3, 0)\) and \((5, 1, 0)\).

Answer

a) Sample answers: \((n, m, c) = (2, 4, 3)\) and \((6, 2, 0)\). In general, \(n, m \in \{2, 4, 6\}\) and \(c \in \mathbb{R}\). b) Sample answers: \((n, m, c) = (1, 3, 0)\) and \((5, 1, 0)\). In general, \(n, m \in \{1, 3, 5\}\) and \(c = 0\).
Even and odd functions 26
Determine algebraically whether the graph of \(f(x) = 3x^6 - 4x^2 + 7\) has y-axis symmetry, origin symmetry, or neither.

Hints

- Substitute \(-x\) for every occurrence of \(x\). - Simplify powers with even exponents. - Compare the result with \(f(x)\) and \(-f(x)\).

Solution

1. Substitute \(-x\) for \(x\): \(f(-x) = 3(-x)^6 - 4(-x)^2 + 7\). 2. Because the exponents \(6\) and \(2\) are even, \(f(-x) = 3x^6 - 4x^2 + 7\). 3. Therefore, \(f(-x) = f(x)\), so \(f\) is even and its graph is symmetric about the y-axis.

Answer

The graph is symmetric about the y-axis because \(f(-x) = f(x)\).
Even and odd functions 27
Determine algebraically whether each polynomial function is even or odd. 1. \(p(x) = 3x^5 - 2x^3 + x\) 2. \(q(x) = x^4 - 2x^2 + 5\)

Hints

- Substitute \(-x\) for every occurrence of \(x\). - Simplify one power at a time. - Compare the result with the original function. - If the result is not the original function, compare it with the opposite of the function.

Solution

1. \(p(-x) = 3(-x)^5 - 2(-x)^3 + (-x) = -3x^5 + 2x^3 - x = -p(x)\). Therefore, \(p\) is odd. 2. \(q(-x) = (-x)^4 - 2(-x)^2 + 5 = x^4 - 2x^2 + 5 = q(x)\). Therefore, \(q\) is even.

Answer

1. \(p\) is odd; its graph is symmetric about the origin. 2. \(q\) is even; its graph is symmetric about the y-axis.
Even and odd functions 28
Determine algebraically whether each function is even, odd, or neither. a) \(f(x)=\frac{e^x+e^{-x}}{2}\) b) \(g(x)=\frac{x^3}{x^2+1}\)

Hints

- Replace \(x\) with \(-x\) in the whole expression. - In a quotient, consider separately how the numerator and denominator change sign. - Compare each simplified expression with the original function and its negative.

Solution

1. For \(f\), substitute \(-x\): \(f(-x)=\frac{e^{-x}+e^x}{2}=f(x)\). Therefore, \(f\) is even, so its graph is symmetric about the y-axis. 2. For \(g\), the denominator is positive for every real input, so the domain is symmetric about \(0\). Also, \(g(-x)=\frac{(-x)^3}{(-x)^2+1}=-\frac{x^3}{x^2+1}=-g(x)\), so \(g\) is odd and has origin symmetry.

Answer

a) Even; symmetric about the y-axis. b) Odd; symmetric about the origin.
Even and odd functions 29
Determine algebraically whether each function is even, odd, or neither. a) \(h(x)=\frac{x^2-4}{x^3}\) b) \(k(x)=2^{x^2}+x\)

Hints

- Test the identities \(f(-x)=f(x)\) and \(f(-x)=-f(x)\). - Think about how an odd power in a denominator changes under \(x\mapsto-x\). - Check the change to the exponent separately from the extra \(x\) term.

Solution

1. For \(h\), the domain excludes \(0\) and is symmetric about \(0\). Also, \(h(-x)=\frac{(-x)^2-4}{(-x)^3}=\frac{x^2-4}{-x^3}=-h(x)\), so \(h\) is odd. 2. For \(k\), \(k(-x)=2^{(-x)^2}-x=2^{x^2}-x\). This is not \(k(x)=2^{x^2}+x\) for nonzero \(x\), nor is it \(-k(x)=-2^{x^2}-x\). Thus \(k\) is neither even nor odd.

Answer

a) Odd; the graph is symmetric about the origin. b) Neither even nor odd.
Even and odd functions 30
Determine whether \(f(x)=x^2\sqrt{x^2+5}\) is even, odd, or neither.

Hints

- Check the domain first. - Replace \(x\) with \(-x\). - Simplify the squared expressions before comparing.

Solution

1. Since \(x^2+5>0\) for every real \(x\), the domain is \(\mathbb{R}\), which is symmetric about \(0\). 2. Substitute \(-x\): \(f(-x)=(-x)^2\sqrt{(-x)^2+5}=x^2\sqrt{x^2+5}=f(x)\). 3. Therefore, \(f\) is even.

Answer

The function is even, so its graph is symmetric about the y-axis.
Even and odd functions 31
Determine whether \(g(x)=\frac{\sqrt{x^4+1}}{x^3}\) is even, odd, or neither.

Hints

- Determine the domain before testing symmetry. - Compare the effects of \(-x\) on the fourth and third powers. - Check whether the result equals \(g(x)\) or \(-g(x)\).

Solution

1. The denominator requires \(x\ne0\), while \(x^4+1>0\) for every real \(x\). Thus, the domain is \(\mathbb{R}\setminus\{0\}\), which is symmetric about \(0\). 2. Substitute \(-x\): \(g(-x)=\frac{\sqrt{(-x)^4+1}}{(-x)^3}=\frac{\sqrt{x^4+1}}{-x^3}=-g(x)\). 3. Therefore, \(g\) is odd.

Answer

The function is odd, so its graph is symmetric about the origin.
Even and odd functions 32
Complete the tables for the power functions \(f(x) = x^4\) and \(g(x) = x^7\). Use the symmetry of each graph. a) <table> <tr><td>\(x\)</td><td>\(f(x)\)</td></tr> <tr><td>\(0.8\)</td><td>\(0.4096\)</td></tr> <tr><td>\(1.5\)</td><td>\(5.0625\)</td></tr> <tr><td>\(-0.8\)</td><td></td></tr> <tr><td>\(-1.5\)</td><td></td></tr> </table> b) <table> <tr><td>\(x\)</td><td>\(g(x)\)</td></tr> <tr><td>\(0.6\)</td><td>\(0.0279936\)</td></tr> <tr><td>\(1.2\)</td><td>\(3.5831808\)</td></tr> <tr><td></td><td>\(-0.0279936\)</td></tr> <tr><td></td><td>\(-3.5831808\)</td></tr> </table>

Hints

- Use the exponent to decide whether each power function is even or odd. - Determine whether changing the sign of \(x\) changes the function value. - For an even function, \(f(-x) = f(x)\). - For an odd function, \(f(-x) = -f(x)\).

Solution

1. The function \(f(x) = x^4\) is even, so \(f(-x) = f(x)\). Therefore, \(f(-0.8) = 0.4096\) and \(f(-1.5) = 5.0625\). 2. The function \(g(x) = x^7\) is odd, so \(g(-x) = -g(x)\). 3. Since \(g(0.6) = 0.0279936\), the input that gives \(-0.0279936\) is \(-0.6\). 4. Since \(g(1.2) = 3.5831808\), the input that gives \(-3.5831808\) is \(-1.2\).

Answer

a) \(f(-0.8) = 0.4096\) and \(f(-1.5) = 5.0625\) b) The missing inputs are \(-0.6\) and \(-1.2\), in that order.
Even and odd functions 33
Let \(f(x)=0.25x^4\). a) Prove from the definition that \(f\) is even. b) The point \((3,20.25)\) lies on the graph. Without substituting \(-3\) into the formula, state the corresponding point required by the symmetry of an even function. c) A classmate says, “Because \(f(0)=0\), this proves that \(f\) is odd as well.” Explain why this reasoning is wrong.

Hints

- Apply the definition of an even function to the formula for an arbitrary input \(x\). - Once evenness is established, think about how y-axis symmetry changes the sign of an x-coordinate. - A single value such as \(f(0)\) cannot establish an identity that must hold for every input.

Solution

1. \(f(-x)=0.25(-x)^4=0.25x^4=f(x)\) for every real \(x\), so \(f\) is even. 2. Even-function symmetry reflects points across the y-axis. Therefore, \((3,20.25)\) requires the point \((-3,20.25)\). 3. The condition \(f(0)=0\) alone does not prove oddness. For example, \(f(1)=0.25\) and \(f(-1)=0.25\), not \(-0.25\). Thus, \(f(-x)=-f(x)\) is not true for all \(x\).

Answer

a) \(f(-x)=f(x)\), so \(f\) is even. b) \((-3,20.25)\) c) Having \(f(0)=0\) is not sufficient for oddness; here \(f(-1)=f(1)=0.25\), so \(f(-1)\ne -f(1)\).
Even and odd functions 34
Let \(f(x)=0.25x^3\). a) Prove from the definition that \(f\) is odd. b) The point \((6,54)\) lies on the graph. Without evaluating \(f(-6)\) directly, state the point required by origin symmetry. c) Explain why checking only \(f(0)=0\) would not, by itself, prove that a function is odd.

Hints

- Replace \(x\) by \(-x\) and compare the result with \(-f(x)\). - Origin symmetry changes the signs of both coordinates. - Distinguish a condition that is necessary at one input from a definition that must hold for every input.

Solution

1. \(f(-x)=0.25(-x)^3=-0.25x^3=-f(x)\) for every real \(x\), so \(f\) is odd. 2. Origin symmetry sends \((x,y)\) to \((-x,-y)\). Therefore, \((6,54)\) requires \((-6,-54)\). 3. Oddness requires \(f(-x)=-f(x)\) for every input in a symmetric domain. The single condition \(f(0)=0\) checks only one input and cannot establish that identity.

Answer

a) \(f(-x)=-f(x)\), so \(f\) is odd. b) \((-6,-54)\) c) The condition \(f(0)=0\) checks only one input; oddness requires \(f(-x)=-f(x)\) for every input in the domain.
Even and odd functions 35
Match each function to graph a, b, or c. Justify your matches using symmetry and a key point such as the y-intercept. \(f(x)=\frac{4x}{x^2+2}\) \(g(x)=-\frac{x^2}{x^2+2}\) \(h(x)=\frac{4}{x^2+2}\)
Figure for problem 532461

Hints

- Test each rule for even or odd symmetry. - Find the y-intercept of each even function to tell them apart. - Use a graph's position above or below the x-axis as a further check.

Solution

1. For \(f\), \(f(-x)=-f(x)\), so its graph has origin symmetry. This matches graph c. 2. For \(g\), \(g(-x)=g(x)\) and \(g(0)=0\). The even graph through the origin that stays nonpositive is graph a. 3. For \(h\), \(h(-x)=h(x)\) and \(h(0)=2\). The even graph above the x-axis with y-intercept \(2\) is graph b.

Answer

Graph a: \(g(x)=-\frac{x^2}{x^2+2}\) Graph b: \(h(x)=\frac{4}{x^2+2}\) Graph c: \(f(x)=\frac{4x}{x^2+2}\)
Even and odd functions 36
Let \(h(x)=-0.2x^3\). a) Prove algebraically that \(h\) is odd. b) The graph marks a point \(A\). Read its coordinates, then, without substituting the opposite input into the formula, use odd symmetry to determine the coordinates of the corresponding point \(B\). c) Explain why the two points in part b demonstrate origin symmetry rather than x-axis or y-axis symmetry.
Figure for problem 533138

Hints

- Prove the parity identity for an arbitrary input before using the marked point. - For an odd function, what happens to both coordinates of a point under the graph symmetry? - Compare the point transformation for origin symmetry with a reflection across a single axis.

Solution

1. \(h(-x)=-0.2(-x)^3=0.2x^3=-h(x)\) for every real \(x\). Therefore, \(h\) is odd. 2. Origin symmetry maps \((x,y)\) to \((-x,-y)\). Thus, \(A(3,-5.4)\) corresponds to \(B(-3,5.4)\). 3. An x-axis reflection would keep the x-coordinate \(3\), while a y-axis reflection would keep the y-coordinate \(-5.4\). Here both coordinate signs change, which is the point transformation for origin symmetry.

Answer

a) \(h(-x)=-h(x)\), so \(h\) is odd. b) \(B=(-3,5.4)\) c) Both coordinate signs change, so the symmetry is about the origin.
Even and odd functions 37
Let \(f(x)=x^3\). a) Solve \(f(x)=-8\). b) How many intersection points does the graph of \(f\) have with the line \(y=5\)? Explain using the graph’s behavior, and state how odd symmetry relates this intersection to the one with \(y=-5\). c) Give an example of a power function \(g(x)=ax^3\) whose graph is vertically compressed compared with \(f\). Is your example even, odd, or neither?
Figure for problem 533477

Hints

- Identify the number whose cube is \(-8\). - Consider how many times a horizontal line can cross a strictly increasing cubic graph, and recall that an odd graph has origin symmetry. - A vertical compression uses a coefficient whose absolute value is between \(0\) and \(1\); test \(g(-x)\) to classify the symmetry.

Solution

1. Solve \(x^3=-8\): \(x=\sqrt[3]{-8}=-2\). 2. The function \(f(x)=x^3\) is strictly increasing and takes every real output value exactly once, so the line \(y=5\) intersects the graph once. Also, \(f(-x)=-f(x)\), so the graph is odd: if \((r, 5)\) is the intersection with \(y=5\), then \((-r, -5)\) is the corresponding intersection with \(y=-5\). 3. A vertical compression occurs when \(0<|a|<1\). One example is \(g(x)=0.5x^3\). Since \(g(-x)=-g(x)\), this function is also odd.

Answer

a) \(x=-2\) b) One intersection point. Odd symmetry gives a corresponding intersection with \(y=-5\) at the opposite x-coordinate. c) Sample answer: \(g(x)=0.5x^3\), which is odd.
Even and odd functions 38
Describe the domain, range, and symmetry of \(f(x)=x^3\) and \(g(x)=x^6\).
Figure for problem 533491

Hints

- Check whether either function has restrictions on its input. - Determine whether each function can produce negative outputs. - Compare \(f(-x)\) with \(f(x)\), and do the same for \(g\).

Solution

1. Both functions are defined for every real input, so both domains are \((-\infty, \infty)\). 2. The cubic function takes every real value, so the range of \(f\) is \((-\infty, \infty)\). The sixth-power function is never negative, so the range of \(g\) is \([0, \infty)\). 3. Since \(f(-x)=-f(x)\), \(f\) is odd and its graph is symmetric about the origin. Since \(g(-x)=g(x)\), \(g\) is even and its graph is symmetric about the y-axis.

Answer

For \(f(x)=x^3\): domain \((-\infty, \infty)\), range \((-\infty, \infty)\), symmetric about the origin For \(g(x)=x^6\): domain \((-\infty, \infty)\), range \([0, \infty)\), symmetric about the y-axis
Even and odd functions 39
Match graphs \(f\), \(g\), and \(h\) to the correct function rules. 1. \(y=x^2\) 2. \(y=x^3\) 3. \(y=\frac{1}{x}\) Justify the matches using symmetry and other visible graph features.
Figure for problem 533496

Hints

- Compare y-axis symmetry with origin symmetry. - Check whether each graph passes through the origin. - Identify the graph that approaches the coordinate axes as asymptotes.

Solution

1. Graph \(g\) is symmetric about the y-axis and has only nonnegative outputs, so it represents \(y=x^2\). 2. Graph \(h\) passes through the origin and is symmetric about the origin, with branches in Quadrants I and III. It represents \(y=x^3\). 3. Graph \(f\) has two separate branches in Quadrants I and III and approaches both coordinate axes without touching them. It represents \(y=\frac{1}{x}\).

Answer

\(f: y=\frac{1}{x}\); \(g: y=x^2\); \(h: y=x^3\)
Even and odd functions 40
A polynomial function has the form \(f(x)=ax^n+c\). Find \(a\), \(n\), and \(c\) so that all conditions are satisfied: - The graph is symmetric about the origin. - The graph passes through \((1,-2)\). - The integer exponent satisfies \(n>1\) and is as small as possible.

Hints

- Use the relationship between origin symmetry and odd functions. - Determine what origin symmetry requires of the constant term. - Substitute the given point to find \(a\).

Solution

1. Symmetry about the origin requires \(f\) to be odd. Therefore, \(n\) must be odd and \(c=0\). 2. Since \((1,-2)\) lies on the graph, \(-2=a(1)^n\), so \(a=-2\). 3. The smallest odd integer greater than \(1\) is \(n=3\). Thus, \(f(x)=-2x^3\).

Answer

\(a=-2\), \(n=3\), and \(c=0\)
Even and odd functions 41
A power function \(f(x)=ax^n\), where \(n\) is a positive integer, passes through \(A(2,16)\) and \(B(-2,16)\). a) Explain why \(n\) must be even. b) Find the function rule when \(n\) is the smallest possible positive integer satisfying this condition.

Hints

- Compare the outputs at opposite inputs. - Which parity of exponent gives y-axis symmetry? - Use the smallest positive even exponent, then substitute one point to find \(a\).

Solution

1. Because \(f(2)=16\), the coefficient \(a\) is nonzero. The two point conditions give \(a2^n=a(-2)^n\), so \(2^n=(-2)^n\). This equality holds only when \(n\) is even. 2. The smallest positive even integer is \(n=2\). 3. Substitute \((2,16)\) into \(f(x)=ax^2\): \(16=a(2^2)=4a\), so \(a=4\). 4. Therefore, \(f(x)=4x^2\).

Answer

a) Since \(a\ne0\) and \(a2^n=a(-2)^n\), \(n\) must be even. b) \(f(x)=4x^2\)
Even and odd functions 42
Match graphs p, q, and r to the functions below. Use symmetry and end behavior to explain your choices. \(a(x)=\frac{2x}{x^2+1}\) \(b(x)=\frac{x^2}{x^2+1}\) \(c(x)=e^{-0.2x^2}\)
Figure for problem 534032

Hints

- Find the graph with origin symmetry first. - For the two even functions, compare their values at \(x=0\). - What height does each even function approach for large positive inputs?

Solution

1. Since \(a(-x)=-a(x)\), \(a\) is odd. The origin-symmetric graph p represents \(a\). 2. Both \(b\) and \(c\) are even. The function \(b\) has \(b(0)=0\) and approaches \(1\) as \(|x|\to\infty\), matching graph q. 3. The function \(c\) has \(c(0)=1\) and approaches \(0\) as \(|x|\to\infty\), matching graph r.

Answer

p: \(a(x)=\frac{2x}{x^2+1}\) q: \(b(x)=\frac{x^2}{x^2+1}\) r: \(c(x)=e^{-0.2x^2}\)
Even and odd functions 43
The displayed graph \(k\) is proposed as the graph of \(g(x)=x^3-3x\). a) Prove algebraically that \(g\) is odd. b) Read the displayed values at \(x=-1\) and \(x=1\). Use them to test whether \(k\) is odd. c) Explain why your parity test is enough to conclude that the displayed graph cannot be the graph of \(g\).
Figure for problem 534323

Hints

- Apply the odd-function definition to \(g\) before looking for other graph features. - Compare the outputs shown at opposite inputs \(-1\) and \(1\). - One violated required symmetry condition is enough to reject the proposed graph.

Solution

1. \(g(-x)=(-x)^3-3(-x)=-x^3+3x=-(x^3-3x)=-g(x)\). Therefore, \(g\) is odd. 2. From the displayed graph, \(k(-1)=4\) and \(k(1)=0\). 3. If \(k\) were odd, then \(k(-1)\) would have to equal \(-k(1)=0\). Since \(4\ne0\), the displayed graph is not odd. 4. The graph of \(g\) must be odd, but the displayed graph is not. Therefore, the displayed graph cannot represent \(g\).

Answer

a) \(g(-x)=-g(x)\), so \(g\) is odd. b) \(k(-1)=4\) and \(k(1)=0\), so \(k(-1)\ne-k(1)\); therefore, \(k\) is not odd. c) An odd function cannot have a graph that fails the odd-function test, so the displayed graph cannot be \(g\).
Even and odd functions 44
Compare graphs a) and b). Which one represents an odd function? Explain why the other one is not odd.
Figure for problem 560699

Hints

- An odd function has symmetry about the origin, not merely a similar-looking curved shape. - Compare what happens at the y-axis in each graph. - What point must every odd function defined at \(0\) pass through?

Solution

1. Graph a) is symmetric about the origin, so it represents an odd function. 2. Graph b) crosses the y-axis at \((0,1)\). An odd function defined at \(0\) must pass through \((0,0)\), so b) is not odd.

Answer

Graph a) is odd. Graph b) is not odd because its value at \(0\) is \(1\), not \(0\).
Even and odd functions 45
Consider \(h(x)=0.1x^4-1.6x^2\). a) Determine algebraically what symmetry the graph has. b) Find all x-intercepts and the y-intercept. c) The graph is shifted right \(2\) units. What is the line of symmetry of the shifted graph?

Hints

- Compare \(h(-x)\) and \(h(x)\) to check symmetry. - Factor the expression to find where its value is zero. - What happens to a vertical line when the entire graph moves right?

Solution

1. \(h(-x)=0.1(-x)^4-1.6(-x)^2=0.1x^4-1.6x^2=h(x)\), so \(h\) is even and its graph is symmetric about the y-axis. 2. \(h(0)=0\), so the y-intercept is \((0, 0)\). 3. Factor to find the zeros: \(0.1x^2(x^2-16)=0\). Thus \(x=0\), \(x=-4\), or \(x=4\), giving x-intercepts \((-4, 0)\), \((0, 0)\), and \((4, 0)\). 4. Shifting the graph right \(2\) units moves its line of symmetry from \(x=0\) to \(x=2\).

Answer

a) Symmetric about the y-axis (even). b) x-intercepts: \((-4, 0)\), \((0, 0)\), and \((4, 0)\); y-intercept: \((0, 0)\) c) \(x=2\)
Even and odd functions 46
A power function has the form \(f(x) = ax^n\). Its graph passes through \(P(1, -2)\) and \(Q(2, -32)\). Find the function rule. Then determine whether the graph is symmetric about the y-axis or symmetric about the origin. Justify your answer using the exponent.

Hints

- Substitute the first point into the general form to find \(a\). - Use the second point and the value of \(a\) to determine \(n\). - How does an even or odd exponent affect a function's symmetry?

Solution

1. Substitute \(P(1, -2)\): \(-2 = a(1)^n\), so \(a = -2\). 2. Substitute \(Q(2, -32)\): \(-32 = -2(2^n)\). 3. Divide by \(-2\): \(16 = 2^n\), so \(n = 4\). Therefore, \(f(x) = -2x^4\). 4. Because \(n=4\) is even, \(f(-x)=f(x)\). The graph is symmetric about the y-axis.

Answer

\(f(x) = -2x^4\). Because the exponent \(4\) is even, the graph is symmetric about the y-axis.
Even and odd functions 47
Diego claims that there is a power function \(f(x)=ax^n\), where \(n\) is a positive integer, with all three properties below: 1. The graph is symmetric about the origin. 2. The graph passes through \(P(2,8)\). 3. The function is strictly decreasing over its entire domain. Determine mathematically whether such a function can exist. Justify your conclusion.

Hints

- Translate the stated symmetry into a condition on a power function's exponent. - Use the given point to determine what must be true about the coefficient. - Check whether those two conditions are compatible with decreasing behavior.

Solution

1. Symmetry about the origin requires \(n\) to be odd. 2. Since the graph passes through \((2,8)\), \(a\cdot2^n=8\), so \(a=\frac{8}{2^n}>0\). 3. A power function \(f(x)=ax^n\) with odd positive integer \(n\) and \(a>0\) is strictly increasing over all real numbers. 4. This contradicts the requirement that the function be strictly decreasing. Therefore, no such function exists.

Answer

No such function exists. Origin symmetry requires an odd exponent, and the point \((2,8)\) forces \(a>0\). That combination produces a strictly increasing function, not a decreasing one.
Even and odd functions 48
Consider the functions \(f(x)=0.25x^4-2x^2+1\), \(g(x)=x^3+2\), and \(h(x)=-x^3+2\). a) Show algebraically that the graph of \(f\) is symmetric about the y-axis. b) Show that the graphs of \(g\) and \(h\) are reflections of each other across the y-axis. c) Explain why the graph of \(g\) itself is not symmetric about the y-axis.

Hints

- Replace every \(x\) with \(-x\). - Distinguish the condition for one graph to be symmetric from the condition for two graphs to be reflections of each other. - Compare \(g(-x)\) with both \(g(x)\) and \(h(x)\).

Solution

1. Replace \(x\) with \(-x\): \(f(-x)=0.25(-x)^4-2(-x)^2+1=0.25x^4-2x^2+1=f(x)\). Therefore, \(f\) is even and its graph is symmetric about the y-axis. 2. Compute \(g(-x)=(-x)^3+2=-x^3+2=h(x)\). Thus, reflecting the graph of \(g\) across the y-axis produces the graph of \(h\). 3. For \(g\) to be symmetric about the y-axis, it would need to satisfy \(g(-x)=g(x)\). Instead, \(-x^3+2\ne x^3+2\) for nonzero \(x\), so \(g\) is not even.

Answer

a) \(f(-x)=f(x)\), so \(f\) is symmetric about the y-axis. b) \(g(-x)=h(x)\), so the graphs of \(g\) and \(h\) are reflections across the y-axis. c) \(g(-x)\ne g(x)\) for nonzero \(x\), so \(g\) is not symmetric about the y-axis.
Even and odd functions 49
Determine whether each function is even, odd, or neither. a) \(f(x)=x(x-2)(x+2)\) b) \(g(x)=(x^2-9)(x^2+1)\) c) \(h(x)=(x-1)^2(x+1)\)

Hints

- Test whether \(p(-x)=p(x)\) or \(p(-x)=-p(x)\). - Simplifying the products may make the powers easier to inspect. - One counterexample is enough to rule out a proposed identity.

Solution

1. For \(f\), simplify to \(f(x)=x(x^2-4)=x^3-4x\). Then \(f(-x)=-x^3+4x=-f(x)\), so \(f\) is odd. 2. For \(g\), \(g(-x)=((-x)^2-9)((-x)^2+1)=(x^2-9)(x^2+1)=g(x)\), so \(g\) is even. 3. For \(h\), neither identity holds. For example, \(h(2)=3\) and \(h(-2)=-9\), so \(h(-2)\ne h(2)\) and \(h(-2)\ne-h(2)\). Therefore, \(h\) is neither even nor odd.

Answer

a) Odd; symmetric about the origin b) Even; symmetric about the y-axis c) Neither even nor odd
Even and odd functions 50
Let \(g(x)=ax+\frac{b}{x}\), with domain \(\mathbb{R}\setminus\{0\}\), where \(a\ne0\) and \(b\ne0\). 1) Show algebraically that \(g(-x)=-g(x)\) for all allowed values of \(a\) and \(b\). 2) Interpret \(g(-x)=-g(x)\) geometrically. 3) Find \(a\) and \(b\) so that the graph passes through \(P(1, 5)\) and \(Q(2, 8.5)\).

Hints

- Replace every \(x\) with \(-x\) and factor out \(-1\). - Connect the identity \(g(-x)=-g(x)\) with odd functions. - Substitute each point to create a system of two equations.

Solution

1. Substitute \(-x\): \(g(-x)=a(-x)+\frac{b}{-x}=-ax-\frac{b}{x}=-\left(ax+\frac{b}{x}\right)=-g(x)\). 2. Therefore, \(g\) is odd, so its graph is symmetric about the origin. 3. The point \(P(1, 5)\) gives \(a+b=5\). The point \(Q(2, 8.5)\) gives \(2a+\frac{b}{2}=8.5\), or \(4a+b=17\). Subtracting the first equation gives \(3a=12\), so \(a=4\). Then \(b=1\).

Answer

1) \(g(-x)=-g(x)\) 2) The graph is symmetric about the origin. 3) \(a=4\) and \(b=1\)
Even and odd functions 51
Classify each function as even, odd, or neither. Briefly explain any answer that is not clear from the simplified expression. 1) \(f(x)=2x^4-x^2+3\) 2) \(f(x)=x^5-2x\) 3) \(f(x)=\frac{2}{x}\) 4) \(f(x)=x^2+x\) 5) \(f(x)=x^6+1\) 6) \(f(x)=4x^3\) 7) \(f(x)=x^4+x^3\) 8) \(f(x)=x^{10}-5\) 9) \(f(x)=x^7+x^5\) 10) \(f(x)=(x+3)^2\) 11) \(f(x)=7x^2\) 12) \(f(x)=x^9\) 13) \(f(x)=1-x^2\) 14) \(f(x)=x-5\) 15) \(f(x)=x^3-x+2\)

Hints

- What happens to a function's output when you replace its input with its opposite? - Does a function's domain also allow the opposite of each input? - How could rewriting a function with parentheses help you check symmetry?

Solution

1. Functions 1, 5, 8, 11, and 13 contain only even powers of \(x\), including constant terms. Thus \(f(-x)=f(x)\), so they are even. 2. Functions 2, 6, 9, and 12 contain only odd powers. Function 3 satisfies \(f(-x)=\frac{2}{-x}=-f(x)\) for every \(x\ne0\). Thus functions 2, 3, 6, 9, and 12 are odd. 3. Functions 4, 7, 14, and 15 contain both even- and odd-power terms, so they are neither. Function 10 expands to \(x^2+6x+9\), so it is also neither.

Answer

1) Even 2) Odd 3) Odd 4) Neither 5) Even 6) Odd 7) Neither 8) Even 9) Odd 10) Neither 11) Even 12) Odd 13) Even 14) Neither 15) Neither
Even and odd functions 52
Let \(f\) be an even function, so \(f(-x)=f(x)\), and let \(g\) be an odd function, so \(g(-x)=-g(x)\). Determine whether \(h(x)=f(x)g(x)\) is even, odd, or neither. Prove your conclusion from the definitions. Then determine the symmetry of \(k(x)=g_1(x)g_2(x)\) when both \(g_1\) and \(g_2\) are odd.

Hints

- Substitute \(-x\) into each product. - Replace each factor using its even or odd identity. - Track the signs when multiplying two negative factors.

Solution

1. For \(h\), \(h(-x)=f(-x)g(-x)=f(x)(-g(x))=-f(x)g(x)=-h(x)\). Therefore, \(h\) is odd. 2. For \(k\), \(k(-x)=g_1(-x)g_2(-x)=(-g_1(x))(-g_2(x))=g_1(x)g_2(x)=k(x)\). Therefore, \(k\) is even.

Answer

\(h\) is odd and symmetric about the origin. \(k\) is even and symmetric about the y-axis.
Even and odd functions 53
Investigate these consequences of even and odd function symmetry. a) A function \(f\) is defined at \(x=0\) and is odd. Explain algebraically why \(f(0)=0\). b) A function \(g\) satisfies \(g(-3)=4\) and \(g(3)=4\). Explain why \(g\) cannot be odd. c) Show that a function that is both even and odd must be the zero function on its domain.

Hints

- Substitute a strategic value into the odd-function identity. - Compare the values at opposite inputs. - Combine the equations for even and odd functions.

Solution

1. Since \(f\) is odd, \(f(-x)=-f(x)\). At \(x=0\), this gives \(f(0)=-f(0)\), so \(2f(0)=0\) and \(f(0)=0\). 2. If \(g\) were odd, \(g(-3)=-g(3)\). The given values would require \(4=-4\), which is impossible. 3. If \(f\) is both even and odd, then \(f(-x)=f(x)\) and \(f(-x)=-f(x)\). Thus, \(f(x)=-f(x)\), so \(2f(x)=0\) and \(f(x)=0\) for every \(x\) in the domain.

Answer

a) \(f(0)=-f(0)\), so \(f(0)=0\). b) Odd symmetry would require \(g(-3)=-g(3)\), but the given values are both \(4\). c) The two identities imply \(f(x)=-f(x)\), so \(f(x)=0\) for every \(x\) in the domain.
Even and odd functions 54
Analyze how translations affect symmetry. a) Suppose \(f\) is even. Use an example, such as a parabola, to show that \(h(x)=f(x-c)\) with \(c\ne0\) is not generally symmetric about the y-axis. b) Suppose \(g\) is odd. Determine algebraically whether \(k(x)=g(x)+d\), where \(d\ne0\), remains symmetric about the origin.

Hints

- Test a simple translated parabola at opposite x-values. - Apply the odd-function identity to \(g(-x)\). - Compare \(k(-x)\) with \(-k(x)\).

Solution

1. Choose \(f(x)=x^2\) and \(c=1\). Then \(h(x)=(x-1)^2\). Since \(h(1)=0\) but \(h(-1)=4\), \(h(-x)=h(x)\) does not hold in general. The translation moves the symmetry axis from \(x=0\) to \(x=1\). 2. Since \(g\) is odd, \(k(-x)=g(-x)+d=-g(x)+d\). However, \(-k(x)=-g(x)-d\). These expressions are equal only when \(d=0\), so for \(d\ne0\), \(k\) is not symmetric about the origin.

Answer

a) For example, \(f(x)=x^2\) is even, but \(h(x)=(x-1)^2\) is not even because \(h(1)=0\ne4=h(-1)\). b) No. For \(d\ne0\), \(k(-x)=-g(x)+d\ne-g(x)-d=-k(x)\).
Even and odd functions 55
Determine the symmetry of each function and justify your answer. a) \(p(x)=|x|+x^2\) b) \(q(x)=\frac{x^3+2x}{x}\), for \(x\ne0\) c) Let \(f_a(x)=x^3+(a+1)x^2-ax\). Find the real value of \(a\) for which \(f_a\) is odd.

Hints

- Compare the expressions after replacing \(x\) with \(-x\). - For the quotient, simplify for the allowed nonzero inputs and check domain symmetry. - In part c), what must happen to the entire expression when the input changes sign?

Solution

1. Since \(|-x|=|x|\) and \((-x)^2=x^2\), \(p(-x)=p(x)\), so \(p\) is even. 2. For \(x\ne0\), \(q(x)=x^2+2\). Its domain excludes \(0\) but includes both members of every other opposite pair. Also, \(q(-x)=(-x)^2+2=q(x)\), so \(q\) is even. 3. For \(f_a\) to be odd, the coefficient of \(x^2\) must be \(0\). Hence \(a+1=0\), so \(a=-1\). Then \(f_{-1}(x)=x^3+x\) is odd.

Answer

a) Even; symmetric about the y-axis b) Even; symmetric about the y-axis on its domain c) \(a=-1\)
Even and odd functions 56
For the rational-function family \(g_k(x)=\frac{x^2+4}{x-k+5}\), determine whether exactly one or more than one real value of \(k\) makes \(g_k\) odd.

Hints

- Use the identity \(g_k(-x)=-g_k(x)\). - The numerator is already even; determine when the denominator is odd. - Check that the resulting domain is symmetric about \(0\).

Solution

1. The numerator \(x^2+4\) is even. For the quotient to be odd, the linear denominator must be odd. 2. Rewrite the denominator as \(x+(5-k)\). A linear function of this form is odd only when its constant term is \(0\). 3. Set \(5-k=0\), which gives \(k=5\). 4. Verification: \(g_5(x)=\frac{x^2+4}{x}=x+\frac{4}{x}\), with domain \(x\ne0\). Both terms are odd, so \(g_5(-x)=-g_5(x)\). 5. Therefore, exactly one value of \(k\) works.

Answer

Exactly one value works: \(k=5\).
Even and odd functions 57
Find the rule of a cubic polynomial \(g\) with all three properties: 1) Its graph is symmetric about the origin. 2) It has a zero at \(x=2\). 3) It passes through \((1, 6)\).

Hints

- Use only odd powers in the general cubic form. - Translate the zero and the point into equations. - Solve the resulting system for the coefficients.

Solution

1. An odd cubic polynomial has the form \(g(x)=ax^3+bx\). 2. The zero at \(x=2\) gives \(8a+2b=0\), or \(4a+b=0\). 3. The point \((1, 6)\) gives \(a+b=6\). 4. Subtracting the second equation from the first relation gives \(3a=-6\), so \(a=-2\). Then \(b=8\). 5. Therefore, \(g(x)=-2x^3+8x\).

Answer

\(g(x)=-2x^3+8x\)
Even and odd functions 58
Let \(f(x)=x^3+(a+2)x^2+bx\), where \(a\) and \(b\) are real. Determine all ordered pairs \((a, b)\) for which \(f\) is odd. Also determine whether any ordered pair makes \(f\) even.

Hints

- Identify the even-power and odd-power terms. - An odd polynomial cannot have a nonzero even-power term. - An even polynomial cannot have a nonzero cubic term.

Solution

1. For \(f\) to be odd, the coefficient of its even-power term must be \(0\). Thus, \(a+2=0\), so \(a=-2\). 2. The coefficient \(b\) multiplies the odd-power term \(x\), so it may be any real number. Therefore, all pairs \((-2, b)\), where \(b\in\mathbb{R}\), make \(f\) odd. 3. For \(f\) to be even, every odd-power coefficient would need to be \(0\). The coefficient of \(x^3\) is fixed at \(1\), so no values of \(a\) and \(b\) can make \(f\) even.

Answer

Odd: all pairs \((-2, b)\) with \(b\in\mathbb{R}\) Even: no ordered pairs
Even and odd functions 59
Let \(f\) be an even polynomial. 1) Explain why every nonzero zero \(x_0\) must have a matching zero at \(-x_0\). 2) Suppose \(f\) has exactly three distinct real zeros. Identify one zero that \(f\) must have and justify your answer. 3) Give one possible rule for an even polynomial with exactly three distinct real zeros.

Hints

- Apply \(f(-x)=f(x)\) at a zero. - Count nonzero zeros in opposite pairs. - Can you choose three zeros that have the required symmetry and build a polynomial with those zeros?

Solution

1. Since \(f\) is even, \(f(-x)=f(x)\). If \(f(x_0)=0\), then \(f(-x_0)=f(x_0)=0\), so nonzero zeros occur in opposite pairs. 2. Three is odd, while the nonzero zeros occur in pairs. Therefore, the unpaired zero must be \(x=0\), which is its own opposite. 3. Choose the distinct zeros \(-1\), \(0\), and \(1\). The even polynomial \(f(x)=x^2(x-1)(x+1)=x^4-x^2\) has exactly those three distinct real zeros.

Answer

1) If \(f(x_0)=0\), then \(f(-x_0)=0\). 2) The function must have the zero \(x=0\). 3) One possible rule is \(f(x)=x^4-x^2\).
Even and odd functions 60
Let \(g\) be an odd polynomial. 1) Prove that \(g(0)=0\). 2) Explain why \(g\) cannot have exactly two distinct real zeros. 3) If \(x=4\) is a zero, list all additional zeros that the symmetry requires.

Hints

- Substitute \(x=0\) into the odd-function identity. - Determine what symmetry does to a nonzero x-intercept. - Count the origin together with opposite pairs.

Solution

1. Odd symmetry gives \(g(-x)=-g(x)\). Setting \(x=0\) yields \(g(0)=-g(0)\), so \(2g(0)=0\) and \(g(0)=0\). 2. Every nonzero zero \(x_0\) has a matching zero \(-x_0\), while \(0\) is always a zero. Thus, the number of distinct real zeros is \(1\) plus an even number, so it cannot equal \(2\). 3. Since \(4\) is a zero, \(-4\) is also a zero. The function must also have the zero \(0\).

Answer

1) \(g(0)=0\) 2) Its distinct real zeros consist of \(0\) and zero or more opposite pairs, so the total cannot be \(2\). 3) The additional required zeros are \(-4\) and \(0\).
Even and odd functions 61
Let \(f(x)=2ax^4+(b-1)x^3+cx^2+4x\). Find \(a\), \(b\), and \(c\) so that \(f\) is odd and its graph passes through \((1, 6)\).

Hints

- Set the coefficients of all even-power terms equal to \(0\). - Substitute the coordinates of the given point. - Solve the remaining linear equation.

Solution

1. For \(f\) to be odd, the coefficients of the even-power terms must be \(0\). Thus, \(2a=0\) and \(c=0\), so \(a=0\) and \(c=0\). 2. The function becomes \(f(x)=(b-1)x^3+4x\). 3. Since \((1, 6)\) lies on the graph, \(6=(b-1)+4=b+3\). 4. Therefore, \(b=3\).

Answer

\(a=0\), \(b=3\), and \(c=0\)
Even and odd functions 62
Determine algebraically whether each function is even, odd, or neither. a) \(f(x)=\frac{x^2+3}{x^4}\) b) \(g(x)=x|x|\) c) \(h(x)=e^x+e^{-x}\) d) \(k(x)=x^3-x+1\)

Hints

- Replace \(x\) with \(-x\) in each rule. - Use \(|-x|=|x|\). - Compare the result with both the original function and its negative.

Solution

1. For \(f\), \(f(-x)=\frac{(-x)^2+3}{(-x)^4}=f(x)\). Its domain excludes \(0\) but is symmetric about \(0\), so \(f\) is even. 2. Since \(|-x|=|x|\), \(g(-x)=(-x)|-x|=-x|x|=-g(x)\). Thus, \(g\) is odd. 3. \(h(-x)=e^{-x}+e^x=h(x)\), so \(h\) is even. 4. \(k(-x)=-x^3+x+1\). This is neither \(k(x)=x^3-x+1\) nor \(-k(x)=-x^3+x-1\), so \(k\) is neither even nor odd.

Answer

a) Even b) Odd c) Even d) Neither even nor odd
Even and odd functions 63
Let \(f(x)=0.4x^n\), where \(n\) is a positive integer. Describe the symmetry, intervals of increase or decrease, and range of \(f\) for even values of \(n\) and for odd values of \(n\).

Hints

- Consider even and odd exponents separately. - Compare \(f(-x)\) with \(f(x)\) and \(-f(x)\). - Use the shapes of familiar graphs such as \(y=x^2\) and \(y=x^3\). - Determine which output values are possible in each case.

Solution

1. If \(n\) is even, then \(f(-x)=0.4(-x)^n=0.4x^n=f(x)\), so \(f\) is even and its graph is symmetric about the y-axis. The function decreases on \((-\infty, 0]\) and increases on \([0, \infty)\). Its range is \([0, \infty)\). 2. If \(n\) is odd, then \(f(-x)=0.4(-x)^n=-0.4x^n=-f(x)\), so \(f\) is odd and its graph has rotational symmetry about the origin. The function increases on \((-\infty, \infty)\), and its range is \((-\infty, \infty)\).

Answer

Even \(n\): even; symmetric about the y-axis; decreasing on \((-\infty, 0]\); increasing on \([0, \infty)\); range \([0, \infty)\). Odd \(n\): odd; rotational symmetry about the origin; increasing on \((-\infty, \infty)\); range \((-\infty, \infty)\).
Even and odd functions 64
Consider the family of power functions \(p(x)=ax^n\), where \(a\ne 0\) is real and \(n\) is a positive integer. a) Determine the conditions on \(a\) and \(n\) that make \(p\) strictly decreasing over its entire domain. b) Does replacing \(a\) with \(-a\) change the graph's type of symmetry? Justify your answer.

Hints

- Compare the overall behavior of \(x^2\) and \(x^3\). - Think about how multiplying all function values by a negative number changes a graph. - Use the definitions of even and odd functions to determine whether the sign of \(a\) affects symmetry.

Solution

1. For odd \(n\), \(x^n\) is strictly increasing on all real numbers. Multiplying by a negative coefficient reverses the order of the outputs, so \(ax^n\) is strictly decreasing exactly when \(n\) is odd and \(a<0\). For even \(n\), the function changes direction at \(x=0\), so it cannot be strictly decreasing over its entire domain. 2. Replacing \(a\) with \(-a\) reflects the graph across the x-axis. The parity of \(n\), not the sign of \(a\), determines the symmetry. When \(n\) is even, both graphs are symmetric about the y-axis. When \(n\) is odd, both graphs have rotational symmetry about the origin.

Answer

a) \(n\) must be odd and \(a<0\). b) No. Replacing \(a\) with \(-a\) reflects the graph across the x-axis but preserves y-axis symmetry for even \(n\) and origin symmetry for odd \(n\).
Even and odd functions 65
Let \(A(z)=z^4-5z^2\) and \(B(z)=z^3-z\). a) Evaluate both functions for \(z=3\) and \(z=-3\). b) For a general real number \(z\), simplify \(A(-z)\) and \(B(-z)\). Use the results to classify \(A\) and \(B\) as even or odd. c) You are told that \(A(2)=-4\) and \(B(2)=6\). Use the classifications from part b to find \(A(-2)\) and \(B(-2)\) without evaluating the powers again.

Hints

- The opposite-input numerical values in part a are evidence, not a general proof. - In part b, substitute \(-z\) into each entire function and simplify. - Use whether the result equals the original function or its negative to classify the function. - Apply that classification directly in part c instead of recomputing the powers.

Solution

1. a) \(A(3)=81-45=36\) and \(A(-3)=81-45=36\). Also, \(B(3)=27-3=24\) and \(B(-3)=-27+3=-24\). 2. b) \(A(-z)=(-z)^4-5(-z)^2=z^4-5z^2=A(z)\), so \(A\) is even. 3. \(B(-z)=(-z)^3-(-z)=-z^3+z=-(z^3-z)=-B(z)\), so \(B\) is odd. 4. c) Since \(A\) is even, \(A(-2)=A(2)=-4\). Since \(B\) is odd, \(B(-2)=-B(2)=-6\).

Answer

a) \(A(3)=A(-3)=36\); \(B(3)=24\), \(B(-3)=-24\) b) \(A(-z)=A(z)\), so \(A\) is even; \(B(-z)=-B(z)\), so \(B\) is odd. c) \(A(-2)=-4\) and \(B(-2)=-6\)
Even and odd functions 66
Consider \(g(x) = (a - 1)x^4 + 2x^3 + (b + 3)x^2 + c\). a) Find \(a\), \(b\), and \(c\) so that the graph of \(g\) is symmetric about the origin. b) Explain why no values of \(a\), \(b\), and \(c\) make the graph symmetric about the y-axis.

Hints

- Identify which powers are even and which are odd. - Determine which coefficients can be changed by choosing \(a\), \(b\), and \(c\). - A term disappears only when its coefficient is zero.

Solution

1. For symmetry about the origin, \(g\) must be odd. Therefore, the coefficients of the even-power terms must be zero. 2. Set \(a - 1 = 0\), \(b + 3 = 0\), and \(c = 0\). This gives \(a = 1\), \(b = -3\), and \(c = 0\). 3. The resulting function is \(g(x) = 2x^3\), which is odd. 4. For symmetry about the y-axis, \(g\) would have to be even, so every odd-power term would need coefficient zero. 5. The coefficient of \(x^3\) is fixed at \(2\), so that term cannot be eliminated. Therefore, no parameter values make \(g\) even.

Answer

a) \(a = 1\), \(b = -3\), and \(c = 0\) b) No such values exist because the fixed term \(2x^3\) prevents the function from being even.
Even and odd functions 67
A function has the form \(f(x) = ax^n + c\), where \(a, c \in \mathbb{R}\) and \(n\) is a positive integer. Determine the conditions on \(a\), \(n\), and \(c\) so that all three statements are true: 1. The graph of \(f\) is symmetric about the y-axis. 2. The graph has y-intercept \((0, 4)\). 3. \(f(x) \to -\infty\) as \(x \to \infty\).

Hints

- Determine which exponents make \(ax^n + c\) an even function. - Evaluate \(f(0)\) to find the y-intercept. - Consider how the sign of \(a\) affects the end behavior when \(n\) is even.

Solution

1. Symmetry about the y-axis requires \(f\) to be even, so \(n\) must be a positive even integer. 2. The y-intercept is determined by \(f(0) = c\). Therefore, \(c = 4\). 3. For a positive even exponent, \(x^n \to \infty\) as \(x \to \infty\). To make \(ax^n + c \to -\infty\), the leading coefficient must satisfy \(a < 0\).

Answer

\(n \in \{2, 4, 6, \ldots\}\), \(c = 4\), and \(a < 0\)
Even and odd functions 68
A polynomial function has the form \(f(x) = ax^3 + bx^2 + cx + d\). a) What must be true about \(b\) and \(d\) for the graph of \(f\) to be symmetric about the origin? Briefly explain. b) Under the condition from part a), find \(a\) and \(c\) if the graph passes through \(P(1, 5)\) and \(Q(2, 22)\).

Hints

- Recall the relationship between origin symmetry and odd functions. - Substitute each point into the function equation. - Solve the resulting system of two linear equations.

Solution

1. Symmetry about the origin means that \(f\) is odd, so only odd powers of \(x\) may have nonzero coefficients. Therefore, \(b = 0\) and \(d = 0\). 2. The function becomes \(f(x) = ax^3 + cx\). Substituting \(P(1, 5)\) gives \(a + c = 5\). 3. Substituting \(Q(2, 22)\) gives \(8a + 2c = 22\), or \(4a + c = 11\). 4. Subtracting \(a + c = 5\) from \(4a + c = 11\) gives \(3a = 6\), so \(a = 2\). 5. Then \(2 + c = 5\), so \(c = 3\).

Answer

a) \(b = 0\) and \(d = 0\), because an odd polynomial contains only odd powers of \(x\). b) \(a = 2\) and \(c = 3\)
Even and odd functions 69
Let \(f(x) = 2x^n + cx^3\), where \(n\) is a positive integer and \(c\) is a real number. The graph of \(f\) must be symmetric about the origin. Its leading term must also be \(-4x^3\), so its end behavior matches that of \(g(x) = -4x^3\). Find all possible values of \(n\) and \(c\).

Hints

- Use the relationship between origin symmetry and odd functions. - Identify which term determines the end behavior. - Consider the cases \(n < 3\), \(n = 3\), and \(n > 3\). - When \(n = 3\), combine the like terms.

Solution

1. Symmetry about the origin requires \(f\) to be odd, so \(n\) must be odd. 2. The leading term must have degree \(3\) and leading coefficient \(-4\). 3. If \(n = 1\), then \(f(x) = 2x + cx^3\). The leading term is \(cx^3\), so \(c = -4\). 4. If \(n = 3\), then \(f(x) = (2 + c)x^3\). Setting \(2 + c = -4\) gives \(c = -6\). 5. If \(n \ge 5\) is odd, then \(2x^n\) has degree greater than \(3\) and becomes the leading term, so the required end behavior is impossible.

Answer

\((n, c) = (1, -4)\) or \((n, c) = (3, -6)\)
Even and odd functions 70
Let \(h(x) = ax^4 + 5x^m\), where \(a\) is a real number and \(m\) is a nonnegative integer. The graph of \(h\) must be symmetric about the y-axis. Its leading term must also be \(5x^4\), so its end behavior matches that of \(p(x) = 5x^4\). Find all possible pairs \((a, m)\).

Hints

- Use the relationship between y-axis symmetry and even functions. - Identify which term determines the end behavior. - Consider the cases \(m < 4\), \(m = 4\), and \(m > 4\). - Remember that \(0\) is an even exponent.

Solution

1. Symmetry about the y-axis requires \(h\) to be even, so \(m\) must be even. 2. If \(m < 4\), then \(m = 0\) or \(m = 2\). The term \(ax^4\) is the leading term, so \(a = 5\). 3. If \(m = 4\), then \(h(x) = (a + 5)x^4\). Setting \(a + 5 = 5\) gives \(a = 0\). 4. If \(m > 4\), then the term \(5x^m\) has degree greater than \(4\), so the leading term cannot be \(5x^4\).

Answer

\((a, m) = (5, 0)\), \((5, 2)\), or \((0, 4)\)
Even and odd functions 71
Let \(p(x) = \frac{1}{4}x^5 - 2x^3\). a) Show algebraically that the graph of \(p\) is symmetric about the origin. b) Describe the symmetry of the graph of \(q(x) = p(x) + 3\). Justify your answer.

Hints

- Use the condition \(f(-x) = -f(x)\) for origin symmetry. - Simplify powers with odd exponents. - Interpret adding \(3\) as a vertical translation. - Track how a vertical translation changes the center of symmetry.

Solution

1. Substitute \(-x\) for \(x\): \(p(-x) = \frac{1}{4}(-x)^5 - 2(-x)^3\). 2. Because \(5\) and \(3\) are odd, \(p(-x) = -\frac{1}{4}x^5 + 2x^3 = -p(x)\). Therefore, the graph of \(p\) is symmetric about the origin. 3. The function \(q(x) = p(x) + 3\) is the graph of \(p\) shifted up \(3\) units. 4. Since \(q(-x) - 3 = p(-x) = -p(x) = -(q(x) - 3)\), the graph of \(q\) is symmetric about the point \((0, 3)\). It is not symmetric about the origin or the y-axis.

Answer

a) \(p(-x) = -p(x)\), so the graph is symmetric about the origin. b) The graph of \(q\) is symmetric about \((0, 3)\).
Even and odd functions 72
The graph of \(f\) is symmetric about the origin. Determine algebraically whether each new function is even or odd. a) \(g(x) = x f(x)\) b) \(h(x) = (f(x))^2\) c) \(k(x) = \frac{1}{2}f(x)\)

Hints

- Begin with \(f(-x) = -f(x)\). - Substitute \(-x\) into each new function. - Compare each result with the original function and its opposite. - Recall that squaring a negative expression gives the same result as squaring the positive expression.

Solution

1. Because \(f\) is odd, \(f(-x) = -f(x)\). 2. For \(g\), \(g(-x) = (-x)f(-x) = (-x)(-f(x)) = xf(x) = g(x)\). Therefore, \(g\) is even. 3. For \(h\), \(h(-x) = (f(-x))^2 = (-f(x))^2 = (f(x))^2 = h(x)\). Therefore, \(h\) is even. 4. For \(k\), \(k(-x) = \frac{1}{2}f(-x) = -\frac{1}{2}f(x) = -k(x)\). Therefore, \(k\) is odd.

Answer

a) Even; the graph is symmetric about the y-axis. b) Even; the graph is symmetric about the y-axis. c) Odd; the graph is symmetric about the origin.
Even and odd functions 73
a) Let \(f\) be an even polynomial function. Determine algebraically whether \(g(x) = xf(x)\) is even or odd. b) Determine whether each constant function is even, odd, both, or neither: \(h(x) = 5\) and \(k(x) = 0\).

Hints

- Use \(f(-x) = f(x)\) for an even function. - Substitute \(-x\) into each function. - Compare the result with both the original function and its opposite. - Pay special attention to the fact that \(-0 = 0\).

Solution

1. Since \(f\) is even, \(f(-x) = f(x)\). Therefore, \(g(-x) = (-x)f(-x) = -xf(x) = -g(x)\), so \(g\) is odd. 2. For \(h(x) = 5\), \(h(-x) = 5 = h(x)\), so \(h\) is even. However, \(h(-x) = 5 \ne -5 = -h(x)\), so \(h\) is not odd. 3. For \(k(x) = 0\), \(k(-x) = 0 = k(x)\) and \(k(-x) = 0 = -k(x)\). Therefore, the zero function is both even and odd.

Answer

a) \(g\) is odd; its graph is symmetric about the origin. b) \(h(x) = 5\) is even but not odd. \(k(x) = 0\) is both even and odd.
Even and odd functions 74
a) The polynomial functions \(p\) and \(q\) are both odd. Prove that their sum \(s(x) = p(x) + q(x)\) is also odd. b) The function \(f(x) = x^3 - 4x\) is shifted up \(3\) units to create \(h\). Determine algebraically whether \(h\) is still odd.

Hints

- Use the defining equation for an odd function. - Substitute \(-x\) into the sum and factor out \(-1\). - A vertical shift changes the function by adding a constant. - Compare \(h(-x)\) directly with \(-h(x)\).

Solution

1. Since \(p\) and \(q\) are odd, \(p(-x) = -p(x)\) and \(q(-x) = -q(x)\). 2. Then \(s(-x) = p(-x) + q(-x) = -p(x) - q(x) = -(p(x) + q(x)) = -s(x)\). Therefore, \(s\) is odd. 3. The shifted function is \(h(x) = x^3 - 4x + 3\). 4. Substituting \(-x\) gives \(h(-x) = -x^3 + 4x + 3\), while \(-h(x) = -x^3 + 4x - 3\). 5. Since \(h(-x) \ne -h(x)\), the shifted function is not odd.

Answer

a) \(s\) is odd because \(s(-x) = -s(x)\). b) No. The function \(h(x) = x^3 - 4x + 3\) is not odd.
Even and odd functions 75
Let \(g(x)=x^3-6x^2+12x-8\), and define the recentered function \(h(u)=g(u+2)\). a) Simplify \(h(u)\). b) Prove from the definition that \(h\) is odd. c) Use the oddness of \(h\) to prove that \(g(2+t)=-g(2-t)\) for every real \(t\), and explain what this says about the graph of \(g\).

Hints

- Recenter the input first; do not test \(g\) itself for oddness about the origin. - Apply the definition of an odd function to the new function \(h\). - Translate the identity for \(h(t)\) and \(h(-t)\) back into statements about \(g\).

Solution

1. Substitute \(u+2\) into \(g\): \(h(u)=g(u+2)=u^3\). 2. Then \(h(-u)=(-u)^3=-u^3=-h(u)\), so \(h\) is odd. 3. Because \(h\) is odd, \(h(t)=-h(-t)\). By the definition of \(h\), this is \(g(2+t)=-g(2-t)\). 4. Inputs equally far to the left and right of \(x=2\) have opposite outputs, so the graph of \(g\) has point symmetry about \((2, 0)\).

Answer

a) \(h(u)=u^3\) b) \(h(-u)=-h(u)\), so \(h\) is odd. c) \(g(2+t)=-g(2-t)\) for every real \(t\); therefore, the graph of \(g\) has point symmetry about \((2, 0)\).
Even and odd functions 76
Determine algebraically whether each polynomial function is even, odd, or neither. 1. \(f(x) = 4x^6 - x^2 + 3\) 2. \(g(x) = -2x^3 - 5x\) 3. \(h(x) = x^4 + x\)

Hints

- Substitute \(-x\) for every occurrence of \(x\). - Track the signs of even and odd powers. - Compare each result with both the original function and its opposite. - Treat a constant as a term with exponent \(0\).

Solution

1. \(f(-x) = 4(-x)^6 - (-x)^2 + 3 = 4x^6 - x^2 + 3 = f(x)\). Therefore, \(f\) is even. 2. \(g(-x) = -2(-x)^3 - 5(-x) = 2x^3 + 5x = -g(x)\). Therefore, \(g\) is odd. 3. \(h(-x) = (-x)^4 + (-x) = x^4 - x\). This is neither \(h(x) = x^4 + x\) nor \(-h(x) = -x^4 - x\). Therefore, \(h\) is neither even nor odd.

Answer

1. Even; the graph is symmetric about the y-axis. 2. Odd; the graph is symmetric about the origin. 3. Neither even nor odd.
Even and odd functions 77
Consider \(f(x) = x^4 + (k - 5)x^3 + mx^2 + (2k - 10)x + 3\). Find all values of \(k\) and \(m\) for which \(f\) is even.

Hints

- Identify the terms with odd exponents. - An even polynomial must have coefficient \(0\) on every odd-power term. - Check whether one value of \(k\) satisfies both odd-power conditions. - Decide whether the coefficient of an even-power term affects evenness.

Solution

1. An even polynomial has no nonzero odd-power terms. 2. Set the coefficient of \(x^3\) equal to zero: \(k - 5 = 0\), so \(k = 5\). 3. With \(k = 5\), the coefficient of \(x\) is \(2k - 10 = 2(5) - 10 = 0\). 4. The term \(mx^2\) has an even exponent, so \(m\) may be any real number.

Answer

\(k = 5\) and \(m\) may be any real number.
Even and odd functions 78
Let \(g(x) = (x + a)x(x - 6)\). a) Find \(a\) so that \(g\) is odd. b) Verify your answer algebraically using the definition of an odd function.

Hints

- Expand the product completely. - Identify the even-power term. - An odd polynomial cannot have a nonzero even-power term. - Substitute \(-x\) into the resulting function to verify the definition.

Solution

1. Expand the expression: \(g(x) = x^3 + (a - 6)x^2 - 6ax\). 2. For \(g\) to be odd, the coefficient of the even-power term \(x^2\) must be zero. Thus, \(a - 6 = 0\), so \(a = 6\). 3. With \(a = 6\), \(g(x) = x^3 - 36x\). 4. Then \(g(-x) = (-x)^3 - 36(-x) = -x^3 + 36x = -(x^3 - 36x) = -g(x)\). Therefore, \(g\) is odd.

Answer

a) \(a = 6\) b) For \(a = 6\), \(g(-x) = -g(x)\), so the graph is symmetric about the origin.
Even and odd functions 79
Disprove the statement with a counterexample: “If a polynomial function is odd, then it has exactly one real zero.” Give a polynomial function that is odd and find all of its real zeros.

Hints

- An odd polynomial may contain only odd powers of \(x\). - To disprove a statement, one valid counterexample is enough. - Look for a polynomial from which you can factor out \(x\). - A cubic polynomial can have as many as three real zeros.

Solution

1. Consider \(f(x) = x^3 - x\). Since \(f(-x) = -f(x)\), the function is odd. 2. Factor the polynomial: \(f(x) = x(x^2 - 1) = x(x - 1)(x + 1)\). 3. By the zero-product property, the real zeros are \(x = -1\), \(x = 0\), and \(x = 1\). 4. This odd polynomial has three real zeros, so the statement is false.

Answer

One counterexample is \(f(x) = x^3 - x\). Its real zeros are \(-1\), \(0\), and \(1\), so it does not have exactly one real zero.
Even and odd functions 80
Let \(f(x)=x^3\) and \(g(x)=-x^3\). a) Complete the value table. <table> <tr> <td>\(x\)</td> <td>\(-2\)</td> <td>\(-1\)</td> <td>\(0\)</td> <td>\(1\)</td> <td>\(2\)</td> </tr> <tr> <td>\(f(x)\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> </tr> <tr> <td>\(g(x)\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> <td>\(\square\)</td> </tr> </table> b) Describe a geometric transformation that maps the graph of \(f\) onto the graph of \(g\). c) Determine algebraically whether \(g\) is even, odd, or neither.

Hints

- Track the sign of a negative number raised to the third power. - Compare the outputs of the two functions for the same input. - Use the tests \(g(-x)=g(x)\) for even functions and \(g(-x)=-g(x)\) for odd functions. - What does a negative sign in front of the entire function do to its graph?

Solution

1. For \(f(x)=x^3\), the values are \(-8,-1,0,1,8\) for \(x=-2,-1,0,1,2\), respectively. 2. For \(g(x)=-x^3\), the values are \(8,1,0,-1,-8\). 3. Multiplying every output of \(f\) by \(-1\) reflects its graph across the x-axis, producing the graph of \(g\). Because \(f\) is odd, reflecting across the y-axis also gives the same graph. 4. \(g(-x)=-(-x)^3=x^3\), while \(-g(x)=-(-x^3)=x^3\). Therefore, \(g(-x)=-g(x)\), so \(g\) is odd.

Answer

a) \(f(x): -8,-1,0,1,8\); \(g(x): 8,1,0,-1,-8\) b) Reflect the graph of \(f\) across the x-axis. For this function, reflection across the y-axis gives the same result. c) \(g\) is odd because \(g(-x)=-g(x)\).
Even and odd functions 81
Let \(f(x)=u(v(x))\). a) Show that if \(u\) is even and \(v\) is odd, then \(f\) is even. b) Determine the symmetry of \(f\) if both \(u\) and \(v\) are odd. Prove your answer. c) Give an example in which \(v\) is neither even nor odd, but \(f=u\circ v\) is even.

Hints

- Use the definitions \(f(-x)=f(x)\) for even functions and \(f(-x)=-f(x)\) for odd functions. - Substitute \(-x\) into the inner function first. - For part c, try using an outer function that reverses a horizontal shift.

Solution

1. If \(v\) is odd, then \(v(-x)=-v(x)\). If \(u\) is even, then \(u(-v(x))=u(v(x))\). Therefore, \(f(-x)=u(v(-x))=u(-v(x))=u(v(x))=f(x)\), so \(f\) is even. 2. If both functions are odd, then \(f(-x)=u(v(-x))=u(-v(x))=-u(v(x))=-f(x)\). Therefore, \(f\) is odd. 3. For example, let \(v(x)=x+1\), which is neither even nor odd, and let \(u(x)=(x-1)^2\). Then \(f(x)=u(v(x))=((x+1)-1)^2=x^2\), which is even.

Answer

a) \(f\) is even. b) \(f\) is odd. c) One example is \(v(x)=x+1\) and \(u(x)=(x-1)^2\), which give \(f(x)=x^2\).
Even and odd functions 82
Symmetry can be preserved or created through function operations. a) Explain why \(h(x)=f(x^4+1)\) is even for every function \(f\) for which the composition is defined. b) Let \(k(x)=(g(x))^2\). Show that \(k\) is even whenever \(g\) is either even or odd. c) For an arbitrary function \(g\), show that \(s(x)=g(x)g(-x)\) is even wherever both factors are defined.

Hints

- Replace \(x\) with \(-x\) and simplify. - Consider the even and odd cases for \(g\) separately in part b. - Use the commutative property of multiplication in part c.

Solution

1. The inner function \(x^4+1\) is even because \((-x)^4+1=x^4+1\). Therefore, \(h(-x)=f((-x)^4+1)=f(x^4+1)=h(x)\). 2. If \(g\) is even, then \(k(-x)=(g(-x))^2=(g(x))^2=k(x)\). If \(g\) is odd, then \(k(-x)=(-g(x))^2=(g(x))^2=k(x)\). Thus \(k\) is even in either case. 3. \(s(-x)=g(-x)g(-(-x))=g(-x)g(x)=g(x)g(-x)=s(x)\). Therefore, \(s\) is even.

Answer

a) \(h(-x)=h(x)\), so \(h\) is even. b) Squaring removes the possible negative sign, so \(k(-x)=k(x)\). c) \(s(-x)=g(-x)g(x)=s(x)\), so \(s\) is even.
Even and odd functions 83
Analyze the function \(g(x)=2^{-x^2+1}\). a) Verify algebraically whether its graph is symmetric about the y-axis. b) Find the coordinates of the highest point on the graph. c) Find the limits of \(g(x)\) as \(x\to\infty\) and as \(x\to-\infty\). Explain the geometric meaning of these limits.

Hints

- Test whether \(g(-x)=g(x)\). - First determine where the exponent \(-x^2+1\) is greatest. - Analyze the exponent as \(|x|\) becomes large.

Solution

1. \(g(-x)=2^{-(-x)^2+1}=2^{-x^2+1}=g(x)\), so \(g\) is even and its graph is symmetric about the y-axis. 2. Because the base \(2\) is greater than \(1\), \(g(x)\) is largest when the exponent \(-x^2+1\) is largest. This occurs at \(x=0\), where \(g(0)=2\). The highest point is \((0, 2)\). 3. As \(x\to\infty\) or \(x\to-\infty\), the exponent \(-x^2+1\to-\infty\). Therefore, \(g(x)\to0\) in both directions. 4. Geometrically, the x-axis, \(y=0\), is a horizontal asymptote on both ends of the graph.

Answer

a) Yes; \(g(-x)=g(x)\), so the graph is symmetric about the y-axis. b) \((0, 2)\) c) \(g(x)\to0\) as \(x\to\infty\) and as \(x\to-\infty\); \(y=0\) is a horizontal asymptote.
Even and odd functions 84
Consider the family of functions \(f_t(x)=e^{tx}+e^{-tx}\), where \(t\in\mathbb{R}\setminus\{0\}\). a) Show algebraically that every graph is symmetric about the y-axis. b) A graph passes through \((2, e^4+e^{-4})\). Find all possible values of \(t\).

Hints

- Test whether \(f_t(-x)=f_t(x)\). - Substitute the given point into the function. - Notice the symmetry between the positive and negative exponents. - Check whether more than one parameter value works.

Solution

1. Evaluate the function at \(-x\): \(f_t(-x)=e^{-tx}+e^{tx}=f_t(x)\). Therefore, each function is even and its graph is symmetric about the y-axis. 2. The point condition gives \(e^{2t}+e^{-2t}=e^4+e^{-4}\). 3. Let \(u=e^{2t}>0\). Then \(u+\frac{1}{u}=e^4+e^{-4}\), whose positive solutions are \(u=e^4\) and \(u=e^{-4}\). 4. Thus, \(2t=4\) or \(2t=-4\), giving \(t=2\) or \(t=-2\).

Answer

a) \(f_t(-x)=f_t(x)\), so each graph is symmetric about the y-axis. b) \(t=2\) or \(t=-2\)
Even and odd functions 85
Find all fifth-degree polynomial functions whose graphs are symmetric about the origin and cross the x-axis at \(x=1\) and \(x=2\).

Hints

- Origin symmetry implies that the polynomial is an odd function. - Zeros of an odd function occur in opposite pairs, along with \(x=0\). - Use factored form to build a polynomial from its zeros. - Include a nonzero leading coefficient to describe all possible functions.

Solution

1. Origin symmetry means the polynomial is odd. Therefore, if \(1\) and \(2\) are zeros, then \(-1\), \(-2\), and \(0\) are also zeros. 2. A fifth-degree polynomial with these five zeros has the form \(f_a(x)=a x(x-1)(x+1)(x-2)(x+2)\), where \(a\ne0\). 3. Simplify: \(f_a(x)=a x(x^2-1)(x^2-4)\) \(=a(x^5-5x^3+4x)\). Every function in this family has degree \(5\), origin symmetry, and the required x-intercepts.

Answer

\(f_a(x)=a(x^5-5x^3+4x)\), where \(a\in\mathbb R\setminus\{0\}\)
Even and odd functions 86
A power function has the form \(h(x)=x^n\). a) Use the table to determine \(n\). b) Use the table to identify the symmetry of the graph. c) Complete the missing entries. The missing input must be positive. <table> <tr><td>\(x\)</td><td>\(h(x)\)</td></tr> <tr><td>\(0.5\)</td><td>\(0.0009765625\)</td></tr> <tr><td>\(-0.5\)</td><td>\(0.0009765625\)</td></tr> <tr><td>\(2\)</td><td>\(1024\)</td></tr> <tr><td>\(-2\)</td><td></td></tr> <tr><td></td><td>\(59{,}049\)</td></tr> <tr><td>\(-3\)</td><td></td></tr> </table>

Hints

- Use the pair of values at \(0.5\) and \(-0.5\) to look for symmetry. - Use the output at \(x=2\) to find the exponent. - Use the sign condition on the missing input and the symmetry to complete the table.

Solution

1. From \(h(2)=1024\), solve \(2^n=1024\). Since \(1024=2^{10}\), \(n=10\). 2. Since \(n=10\) is even, \(h(-x)=h(x)\), so the graph is symmetric about the y-axis. 3. Therefore, \(h(-2)=h(2)=1024\). 4. Since \(3^{10}=59{,}049\), the missing positive input is \(3\). 5. By even symmetry, \(h(-3)=h(3)=59{,}049\).

Answer

a) \(n=10\) b) The graph is symmetric about the y-axis. c) The missing entries from top to bottom are \(1024\), \(3\), and \(59{,}049\).
Even and odd functions 87
Let \(g(x)=x^3+3x^2+3x+5\). A classmate says, “The graph is an odd-function graph because the leading term is \(x^3\).” a) Show that \(g\) itself is not odd. b) Define \(h(u)=g(u-1)-4\). Simplify \(h\) and prove that \(h\) is odd. c) Explain why part b shows that the graph of \(g\) has the symmetry of an odd function after a translation, even though \(g\) is not an odd function.

Hints

- A leading odd power does not by itself make an entire polynomial odd. - Use a necessary property of odd functions to test \(g\) before recentering it. - Simplify the translated function \(h\) and then apply the odd-function definition to \(h\).

Solution

1. An odd function must satisfy \(g(-x)=-g(x)\). Here \(g(0)=5\ne0\), so \(g\) cannot be odd. 2. Substitute \(u-1\): \(h(u)=g(u-1)-4=((u-1)+1)^3+4-4=u^3\). 3. Since \(h(-u)=(-u)^3=-u^3=-h(u)\), the recentered function \(h\) is odd. 4. The transformation \(h(u)=g(u-1)-4\) moves the point \((-1, 4)\) of the original coordinate system to the origin. Since the recentered graph is odd, the original graph has point symmetry about \((-1, 4)\), but it is not symmetric about the origin and therefore is not itself an odd function.

Answer

a) \(g\) is not odd; for example, \(g(0)=5\ne0\). b) \(h(u)=u^3\), so \(h\) is odd. c) The graph of \(g\) is a translated odd-function graph with center \((-1, 4)\), but \(g\) itself is not odd because its symmetry center is not the origin.
Even and odd functions 88
Let \(f(x)=x^3+(k-5)x^2-36x\). Choose \(k\) so that \(f\) is odd. State the symmetry and find all real zeros for that value of \(k\).

Hints

- Eliminate the even-power term. - Factor out \(x\) after substituting the parameter value. - Use the difference of squares.

Solution

1. For the polynomial to be odd, the coefficient of the even-power term must be \(0\): \(k-5=0\), so \(k=5\). 2. Then \(f(x)=x^3-36x\), which is odd and has a graph symmetric about the origin. 3. Factor the equation \(x^3-36x=0\): \(x(x^2-36)=x(x-6)(x+6)=0\). 4. The real zeros are \(-6\), \(0\), and \(6\).

Answer

\(k=5\); the graph is symmetric about the origin; the real zeros are \(x=-6, 0, 6\).
Even and odd functions 89
Let \(g(x)=x^4+(a+1)x-81\). Choose \(a\) so that \(g\) is even. State the symmetry and find all real zeros for that value of \(a\).

Hints

- Eliminate the odd-power term. - Set the resulting polynomial equal to \(0\). - Remember that an even power can produce two real roots.

Solution

1. For the polynomial to be even, the coefficient of the linear term must be \(0\): \(a+1=0\), so \(a=-1\). 2. Then \(g(x)=x^4-81\), which is even and has a graph symmetric about the y-axis. 3. Set \(x^4-81=0\). Then \(x^4=81\), so the real solutions are \(x=3\) and \(x=-3\).

Answer

\(a=-1\); the graph is symmetric about the y-axis; the real zeros are \(x=-3\) and \(x=3\).
Even and odd functions 90
For each polynomial, determine whether its graph is symmetric about the y-axis, symmetric about the origin, or neither. Then determine its end behavior as \(x\to\infty\) and \(x\to-\infty\). a) \(f(x)=-x^4+10x^2-5\) b) \(g(x)=0.5x^5-2x^3+x\) c) \(h(x)=-x^3+x^2-1\)

Hints

- Compare \(p(-x)\) with \(p(x)\) and \(-p(x)\). - A polynomial with only even powers is even; one with only odd powers is odd. - Use the leading term to determine the end behavior.

Solution

1. The function \(f\) contains only even powers of \(x\), so \(f(-x)=f(x)\). Its graph is symmetric about the y-axis. Its leading term is \(-x^4\), so both ends fall toward \(-\infty\). 2. The function \(g\) contains only odd powers of \(x\), so \(g(-x)=-g(x)\). Its graph is symmetric about the origin. Its leading term is \(0.5x^5\), so the left end falls and the right end rises. 3. The function \(h\) contains both even and odd powers, so it is neither even nor odd. Its leading term is \(-x^3\), so the left end rises and the right end falls.

Answer

a) Symmetric about the y-axis; \(\lim_{x\to\infty}f(x)=-\infty\) and \(\lim_{x\to-\infty}f(x)=-\infty\). b) Symmetric about the origin; \(\lim_{x\to\infty}g(x)=\infty\) and \(\lim_{x\to-\infty}g(x)=-\infty\). c) Neither; \(\lim_{x\to\infty}h(x)=-\infty\) and \(\lim_{x\to-\infty}h(x)=\infty\).
Even and odd functions 91
Find equations for the two graphed polynomial functions in the forms \(f(x)=ax^4+bx^2+c\) and \(g(x)=dx^3+ex\).
Figure for problem 532459

Hints

- Use symmetry to decide which powers may appear in each rule. - Read the zeros from the graphs and express each polynomial using factors. - Use the marked point on each graph to find its leading coefficient. - Expand the factored rules into the requested forms.

Solution

1. The zeros of \(f\) are \(x=-2,-1,1,2\). Y-axis symmetry pairs them, so \(f(x)=A(x^2-1)(x^2-4)\). 2. From \(P(0,2)\), \(2=A(-1)(-4)=4A\), so \(A=0.5\). Thus \(f(x)=0.5x^4-2.5x^2+2\). 3. The zeros of \(g\) are \(x=-3,0,3\). Its origin symmetry is consistent with \(g(x)=Bx(x^2-9)\). 4. From \(Q(2,-2)\), \(-2=B\cdot2(4-9)=-10B\), so \(B=0.2\). Thus \(g(x)=0.2x^3-1.8x\).

Answer

\(f(x)=0.5x^4-2.5x^2+2\) \(g(x)=0.2x^3-1.8x\)
Even and odd functions 92
Match each function to graph a, b, or c. First classify each function as even, odd, or neither. Then use symmetry, end behavior, or a key point to justify each match. \(f_1(x)=xe^{-x}\) \(f_2(x)=\frac{1}{2}x^3-\frac{3}{2}x\) \(f_3(x)=\frac{4}{x^2+1}-1\)
Figure for problem 532764

Hints

- Compute \(f(-x)\) for each function. - Compare \(f(-x)\) with both \(f(x)\) and \(-f(x)\). - Use one additional feature, such as an intercept or end behavior, to confirm each match.

Solution

1. For \(f_1\), \(f_1(-x)=-xe^x\), which is neither \(f_1(x)\) nor \(-f_1(x)\). Thus, \(f_1\) is neither even nor odd. Also, \(f_1(x)>0\) for \(x>0\), \(f_1(x)<0\) for \(x<0\), and \(f_1(x)\to0\) as \(x\to\infty\). These features match graph c. 2. For \(f_2\), \(f_2(-x)=-f_2(x)\), so \(f_2\) is odd. Its graph has rotational symmetry about the origin and passes through \((-1,1)\), \((0,0)\), and \((1,-1)\). These features match graph a. 3. For \(f_3\), \(f_3(-x)=f_3(x)\), so \(f_3\) is even. Its graph is symmetric about the y-axis, has y-intercept \((0,3)\), and approaches the horizontal asymptote \(y=-1\). These features match graph b.

Answer

\(f_1\): neither, graph c; \(f_2\): odd, graph a; \(f_3\): even, graph b
Even and odd functions 93
Consider \(f(x)=-0.25x^4\). 1. Describe the graph's shape and symmetry. 2. State the range of \(f\). 3. How would the symmetry and range change for \(g(x)=0.25x^3\)? Describe the differences without drawing a new graph.
Figure for problem 533468

Hints

- Compare the effects of even and odd exponents on symmetry. - Determine whether each function can have positive, negative, or all real outputs. - Use the sign of the coefficient to identify whether the even-power graph opens upward or downward.

Solution

1. The graph of \(f\) opens downward, has a maximum at \((0, 0)\), and is symmetric about the y-axis because its degree is even. 2. Since \(-0.25x^4\le0\), the range is \((-\infty, 0]\). 3. The function \(g\) has odd degree, so its graph is symmetric about the origin. Its outputs cover all real numbers, so its range is \((-\infty, \infty)\).

Answer

1. The graph opens downward, has a maximum at \((0, 0)\), and is symmetric about the y-axis. 2. \((-\infty, 0]\) 3. The graph of \(g\) is symmetric about the origin and has range \((-\infty, \infty)\).
Even and odd functions 94
Match graphs \(u\), \(v\), and \(w\) to \(y=x^2\), \(y=x^4\), and \(y=x^6\). a) Show that all three functions are even. b) Putri says, “Y-axis symmetry tells us which graph is \(x^6\).” Explain why she is mistaken. c) Compare the curves for \(0<x<1\) to justify your matches.
Figure for problem 533478

Hints

- Apply the even-function definition to each exponent. - Is a property helpful for distinguishing choices when every choice has it? - Between \(0\) and \(1\), how do powers change as the exponent grows?

Solution

1. For each \(n\in\{2,4,6\}\), \((-x)^n=x^n\), so all three functions are even. 2. All three graphs have y-axis symmetry, so that feature alone cannot distinguish them. 3. For \(0<x<1\), larger positive exponents produce smaller outputs: \(x^2>x^4>x^6\). 4. On that interval, graph \(u\) is highest, \(v\) is in the middle, and \(w\) is lowest. Thus, \(u=x^2\), \(v=x^4\), and \(w=x^6\).

Answer

a) All three are even because \((-x)^n=x^n\) for their even exponents. b) Y-axis symmetry is shared by all three, so it cannot identify just one. c) \(u=x^2\), \(v=x^4\), and \(w=x^6\).
Even and odd functions 95
Mamadou checks \(f(-2)=-f(2)\) for \(f(x)=0.5x^3\) and concludes that \(f\) is odd. a) Explain why checking one opposite-input pair is not enough to prove that a function is odd. b) Prove algebraically that this function is odd for every real \(x\). c) Given that \(f(6)=108\), use odd symmetry, not direct substitution, to determine \(f(-6)\).

Hints

- Ask whether one numerical example can establish a statement for every real input. - Apply the defining odd-function equation to an arbitrary \(x\). - Once oddness is proved, use the relationship between outputs at opposite inputs.

Solution

1. One pair only verifies the odd-function relation at one input. The definition must hold for every input in the domain. 2. \(f(-x)=0.5(-x)^3=-0.5x^3=-f(x)\) for every real \(x\). Therefore, \(f\) is odd. 3. For an odd function, \(f(-6)=-f(6)=-108\).

Answer

a) One pair does not prove an identity that must hold for every input. b) \(f(-x)=-f(x)\) for every real \(x\), so \(f\) is odd. c) \(f(-6)=-108\)
Even and odd functions 96
The graph shows an even function \(f\) and an odd function \(g\). Let \(h(x)=f(x)+g(x)\). a) Is \(h\) symmetric about the y-axis? Explain. b) Find \(h(0)\) using the graph of \(f\) and the symmetry of \(g\). c) Besides the origin, \(h\) has one more zero. Explain how to locate it using only the graphs of \(f\) and \(g\).
Figure for problem 533588

Hints

- Write \(h(-x)\) using the even and odd identities. - Recall the value of an odd function at \(0\). - A zero of the sum occurs when the two addends are opposites.

Solution

1. Since \(f\) is even and \(g\) is odd, \(h(-x)=f(x)-g(x)\), which is generally not equal to \(h(x)=f(x)+g(x)\). The displayed graph confirms that \(h\) is not symmetric about the y-axis. 2. Every odd function satisfies \(g(0)=0\). The graph shows \(f(0)=0\), so \(h(0)=f(0)+g(0)=0\). 3. A zero of \(h\) satisfies \(f(x)+g(x)=0\), or \(f(x)=-g(x)\). On the graph, look for an x-value where the two function values have equal magnitude and opposite signs. This occurs at \(x=-2.5\).

Answer

a) No. In general, \(h(-x)=f(x)-g(x)\ne h(x)\). b) \(h(0)=0\) c) Find where \(f(x)=-g(x)\). The additional zero is \(x=-2.5\).
Even and odd functions 97
Let \(f(x)=x^3\). Define \(r_x(x)=-f(x)\), which reflects the graph of \(f\) across the x-axis, and \(r_y(x)=f(-x)\), which reflects it across the y-axis. a) Prove that \(f\) is odd. b) Use oddness, rather than separately expanding both transformed formulas, to prove that \(r_x(x)=r_y(x)\) for every real \(x\). c) Explain the geometric meaning of part b and state the quadrants occupied by the common reflected graph, apart from the origin.

Hints

- Establish the odd-function identity before comparing the two reflections. - Translate each geometric reflection into its function notation. - Part b can be completed directly from \(f(-x)=-f(x)\).

Solution

1. \(f(-x)=(-x)^3=-x^3=-f(x)\), so \(f\) is odd. 2. Because \(f\) is odd, \(f(-x)=-f(x)\). Therefore, \(r_y(x)=f(-x)=-f(x)=r_x(x)\) for every real \(x\). 3. Thus, for this odd function, reflecting the graph across the x-axis or across the y-axis produces the same graph. 4. The common reflected graph is \(y=-x^3\). For \(x<0\), the output is positive, and for \(x>0\), the output is negative. Therefore, the graph lies in Quadrants II and IV, apart from the origin.

Answer

a) \(f\) is odd. b) \(r_x(x)=r_y(x)\) for every real \(x\). c) The x-axis and y-axis reflections coincide; the reflected graph lies in Quadrants II and IV and passes through the origin.
Even and odd functions 98
Consider the family of polynomial functions \(g_n(x)=\frac{1}{10}(x^n-16x^{n-2})\) for integers \(n\ge3\). a) Find all zeros of \(g_3\) and \(g_4\), including their multiplicities. b) Determine whether \(g_3\) and \(g_4\) are even, odd, or neither. c) Predict the symmetry of the graph of \(g_5\), and justify your answer from its equation.

Hints

- Can you rewrite the family expression in a form that makes its zeros easier to see? - Use the exponent on each factor to determine multiplicity. - Compare the exponents in each expanded function to the definitions of even and odd functions.

Solution

1. Factor \(g_n(x)=\frac{1}{10}x^{n-2}(x^2-16)=\frac{1}{10}x^{n-2}(x-4)(x+4)\). For \(g_3\), the zeros \(-4\), \(0\), and \(4\) each have multiplicity \(1\). 2. For \(g_4\), the zero \(0\) has multiplicity \(2\), while \(-4\) and \(4\) each have multiplicity \(1\). 3. \(g_3(x)=\frac{1}{10}(x^3-16x)\) has only odd powers, so it is odd. \(g_4(x)=\frac{1}{10}(x^4-16x^2)\) has only even powers, so it is even. 4. \(g_5(x)=\frac{1}{10}(x^5-16x^3)\) has only odd powers, so it is odd and its graph is symmetric about the origin.

Answer

a) \(g_3\): zeros \(-4\), \(0\), \(4\), each of multiplicity \(1\); \(g_4\): zeros \(-4\) and \(4\) of multiplicity \(1\), and \(0\) of multiplicity \(2\). b) \(g_3\) is odd; \(g_4\) is even. c) \(g_5\) is odd; its graph has origin symmetry.
Even and odd functions 99
Match panels a, b, and c to these functions. Explain your choices using symmetry. - \(f(x)=0.1x^4-2x^2+3\) - \(g(x)=0.2x^3-4x\) - \(h(x)=0.2x^3-x^2+2\)
Figure for problem 533644

Hints

- Compare the output at a positive input with the output at its opposite. - How does symmetry about the y-axis differ from symmetry about the origin? - Check the algebraic rule and the graph for the same kind of symmetry.

Solution

1. Function \(h\) has both even- and odd-power terms, so it is neither even nor odd. It matches panel a, which has neither y-axis nor origin symmetry. 2. Function \(f\) has only even powers, so it is even. The y-axis-symmetric graph in panel b matches \(f\). 3. Function \(g\) has only odd powers, so it is odd. The origin-symmetric graph in panel c matches \(g\).

Answer

a: \(h\) b: \(f\) c: \(g\)
Even and odd functions 100
The graph shows an even fourth-degree polynomial \(f\). Find its equation using the marked points.
Figure for problem 534055

Hints

- Which powers can occur in an even fourth-degree polynomial? - How many coefficients must you determine from the graph? - What equations do the marked input-output pairs give you?

Solution

1. Since \(f\) is even and fourth degree, write \(f(x)=ax^4+bx^2+c\). 2. The point \(A(0, 1)\) gives \(c=1\). 3. The point \(B(1, -2)\) gives \(a+b+1=-2\), so \(a+b=-3\). 4. The point \(C(2, 1)\) gives \(16a+4b+1=1\), so \(4a+b=0\). 5. Subtracting the equations gives \(3a=3\), so \(a=1\) and \(b=-4\). 6. Thus, \(f(x)=x^4-4x^2+1\).

Answer

\(f(x)=x^4-4x^2+1\)
Even and odd functions 101
The graph shows an odd cubic polynomial \(g\). Find its equation using the marked points.
Figure for problem 534056

Hints

- An odd cubic has no nonzero even-power or constant terms. - Read the marked coordinates and substitute them into the rule. - Solve the resulting pair of equations.

Solution

1. An odd cubic polynomial has the form \(g(x)=ax^3+bx\). 2. The point \(Q(2,0)\) gives \(8a+2b=0\), or \(4a+b=0\). 3. The point \(P(1,-3)\) gives \(a+b=-3\). 4. Subtracting the second equation from the first gives \(3a=3\), so \(a=1\), \(b=-4\). 5. Thus, \(g(x)=x^3-4x\).

Answer

\(g(x)=x^3-4x\)
Even and odd functions 102
Match graphs r, s, and t to \(k(x)=x^4\), \(m(x)=x^3\), and \(p(x)=x^{-2}\). a) First decide whether the exponent for each graph is even or odd. b) Give the matches and explain how the graphs differ.
Figure for problem 534564

Hints

- Compare y-axis and origin symmetry. - Which graph does not have a value at \(x=0\)? - Compare the behavior near the origin and for large output values.

Solution

1. Graph r is symmetric about the y-axis, so its exponent is even. Graph s has origin symmetry, so its exponent is odd. Graph t has y-axis symmetry, so its exponent is even. 2. Graph r passes through the origin and matches \(k(x)=x^4\). Graph s matches \(m(x)=x^3\). 3. Graph t is undefined at \(x=0\) and approaches the coordinate axes, so it matches \(p(x)=x^{-2}\).

Answer

a) r: even; s: odd; t: even b) r: \(k(x)=x^4\); s: \(m(x)=x^3\); t: \(p(x)=x^{-2}\)
Even and odd functions 103
Match graphs a), b), and c) to the functions below. First classify each function as even, odd, or neither. Then use intercepts, domain, or asymptotic behavior to complete each match. 1) \(f(x)=3e^{-0.5x^2}\) 2) \(g(x)=\frac{x^2-1}{x^2+1}\) 3) \(h(x)=2\ln(x)\)
Figure for problem 534602

Hints

- Check whether each domain is symmetric about zero. - Compare \(f(-x)\) with \(f(x)\) and \(-f(x)\). - Use zeros and asymptotes to distinguish functions with the same symmetry.

Solution

1. The function \(f\) is even because \(f(-x)=f(x)\). Its graph is symmetric about the y-axis, has a maximum at \((0, 3)\), and approaches \(y=0\) as \(x\to\pm\infty\). This matches graph a). 2. The function \(g\) is even because \(g(-x)=g(x)\). It has zeros at \(x=\pm1\) and approaches the horizontal asymptote \(y=1\) as \(|x|\to\infty\). This matches graph b). 3. The function \(h\) is neither even nor odd because its domain is \((0, \infty)\), which is not symmetric about zero. It has a zero at \(x=1\) and a vertical asymptote at \(x=0\). This matches graph c).

Answer

a) \(\rightarrow\) 1), even; b) \(\rightarrow\) 2), even; c) \(\rightarrow\) 3), neither
Even and odd functions 104
Use the graph of the polynomial \(g\). 1. State the least possible degree of \(g\) and explain why. 2. Use its symmetry to write a general polynomial rule of that degree. 3. Find an equation for \(g\) using its zeros and the marked point.
Figure for problem 534854

Hints

- Count the turning points and inspect the graph's end behavior. - Use origin symmetry to restrict the types of terms in the rule. - Read the zeros from the graph to build a factored expression. - Use the marked point to determine the multiplier.

Solution

1. The graph has two turning points, so its degree is at least \(3\). A cubic is consistent with the visible end behavior. 2. The graph has origin symmetry, so it is odd. A cubic with that symmetry has the form \(g(x)=ax^3+cx\). 3. The zeros are \(-3,0,3\), giving \(g(x)=a x(x+3)(x-3)=a(x^3-9x)\). 4. From \(P(1,-2)\), \(-2=a(1-9)=-8a\), so \(a=\frac{1}{4}\). Therefore, \(g(x)=\frac{1}{4}x^3-\frac{9}{4}x\).

Answer

1. Least possible degree: \(3\) 2. \(g(x)=ax^3+cx\) 3. \(g(x)=\frac{1}{4}x^3-\frac{9}{4}x\)
Even and odd functions 105
a) Which of the graphed functions \(f\), \(g\), and \(h\) is even? Explain using symmetry. b) Which function is odd? c) Why is \(h\) not odd even though it has rotational symmetry?
Figure for problem 534974

Hints

- What kind of symmetry must an even graph have? - Where must the center of symmetry of an odd graph be? - Locate the actual center of rotational symmetry for \(h\).

Solution

1. The graph of \(f\) is symmetric about the y-axis, so \(f\) is even. 2. The graph of \(g\) is a line through the origin, so \(g\) is odd. 3. The graph of \(h\) has rotational symmetry about \((0,2)\), not about the origin. For an odd function, opposite inputs must have opposite outputs. Thus, \(h\) is not odd.

Answer

a) \(f\) is even. b) \(g\) is odd. c) \(h\) is symmetric about \((0,2)\), not the origin, so it is not odd.
Even and odd functions 106
Consider \(h(x)=\frac{6}{x^2+2}\). a) Find the domain and range of \(h\). b) Use the formula to explain why the graph is symmetric about the y-axis.
Figure for problem 535015

Hints

- Determine whether the denominator can equal zero. - Find the smallest possible denominator and consider what happens as \(|x|\) becomes large. - Compute \(h(-x)\).

Solution

1. Since \(x^2+2\ge2\), the denominator is never zero. Therefore, the domain is \(\mathbb{R}\). 2. The denominator is smallest at \(x=0\), so the maximum output is \(h(0)=3\). The function is always positive, and \(h(x)\to0\) as \(|x|\to\infty\), but it never equals \(0\). Thus, the range is \((0, 3]\). 3. Replace \(x\) with \(-x\): \(h(-x)=\frac{6}{(-x)^2+2}=\frac{6}{x^2+2}=h(x)\). Therefore, \(h\) is even and its graph is symmetric about the y-axis.

Answer

a) Domain: \(\mathbb{R}\); range: \((0, 3]\) b) \(h(-x)=h(x)\), so \(h\) is even.
Even and odd functions 107
A student says, “If \(f(0)=0\) and \(f(-2)=-f(2)\), then \(f\) is odd.” Is this always true? Use \(f(x)=x^2(x^2-4)\) to support your answer.

Hints

- Check the two conditions using the provided formula. - To show a claim is false, find one pair of opposite inputs that does not follow the odd-function rule. - Try inputs other than the ones already named in the claim.

Solution

1. The function satisfies \(f(0)=0\), \(f(-2)=0\), and \(f(2)=0\). Thus both conditions in the claim hold. 2. But \(f(-1)=-3\) and \(f(1)=-3\), so \(f(-1)\ne-f(1)\). 3. The function is not odd, and the student's claim is false. Checking a few inputs is not enough to prove oddness for all inputs.

Answer

False. This function meets the two given conditions but is not odd: \(f(-1)=f(1)=-3\), not opposite values.
Even and odd functions 108
Andrei claims, “If the graphs of \(f\) and \(g\) are reflections of each other across the y-axis, then each graph must also be symmetric about the y-axis.” Evaluate the claim. State the mathematical condition for each type of symmetry and give a counterexample using two functions.

Hints

- Distinguish a graph being symmetric with itself from two different graphs being mirror images. - Write the algebraic condition for each relationship separately. - A counterexample only needs two reflected functions for which neither function has y-axis symmetry by itself.

Solution

1. The claim is false. 2. A single graph is symmetric about the y-axis when its domain is symmetric about \(0\) and \(f(-x)=f(x)\) for every \(x\) in the domain. 3. Two graphs are reflections of each other across the y-axis when their domains are reflected across \(0\) and \(g(x)=f(-x)\). 4. Let \(f(x)=x+1\) and \(g(x)=-x+1\). Since \(f(-x)=-x+1=g(x)\), the graphs are reflections of each other. However, \(f(-x)\ne f(x)\) and \(g(-x)\ne g(x)\) in general, so neither graph is individually symmetric about the y-axis.

Answer

The claim is false. Individual y-axis symmetry requires \(f(-x)=f(x)\). Two graphs are reflections across the y-axis when \(g(x)=f(-x)\), with correspondingly reflected domains. For example, \(f(x)=x+1\) and \(g(x)=-x+1\) are reflections of each other, but neither function is even.
Even and odd functions 109
Evaluate this statement and justify your conclusion: “If a nonzero odd polynomial is shifted vertically by adding a nonzero constant \(c\), the new function is neither odd nor even.”

Hints

- Define the shifted function and test both symmetry identities. - Compare \(g(-x)\) with \(-g(x)\). - For even symmetry, determine what \(-f(x)=f(x)\) would imply.

Solution

1. Let \(f\) be a nonzero odd polynomial, so \(f(-x)=-f(x)\), and define \(g(x)=f(x)+c\) with \(c\ne0\). 2. For odd symmetry, \(g(-x)=-f(x)+c\), while \(-g(x)=-f(x)-c\). These are equal only if \(c=0\), so \(g\) is not odd. 3. For even symmetry, \(g(-x)=g(x)\) would require \(-f(x)+c=f(x)+c\), or \(f(x)=0\) for every \(x\). 4. That would make \(f\) the zero polynomial, contrary to the hypothesis. Therefore, \(g\) is not even. 5. The statement is true.

Answer

The statement is true. A nonzero vertical shift destroys odd symmetry, and the shifted function could be even only if the original odd polynomial were the zero polynomial.
Even and odd functions 110
Let \(f\) be a nonconstant even polynomial function. Determine whether each new function is even, odd, or neither. Justify each answer algebraically. a) \(p(x) = xf(x)\) b) \(q(x) = f(x) + x^2\) c) \(r(x) = f(x + 1)\)

Hints

- Begin with \(f(-x) = f(x)\). - Test the definitions of even and odd functions for parts a) and b). - For part c), remember that a nonconstant even polynomial has even degree. - Consider what the horizontal shift does to the next-highest power in the leading term.

Solution

1. Because \(f\) is even, \(f(-x) = f(x)\). 2. For \(p\), \(p(-x) = (-x)f(-x) = -xf(x) = -p(x)\). Therefore, \(p\) is odd. 3. For \(q\), \(q(-x) = f(-x) + (-x)^2 = f(x) + x^2 = q(x)\). Therefore, \(q\) is even. 4. Since \(f\) is a nonconstant even polynomial, its degree is an even number \(2n\). The translated polynomial \(r(x) = f(x + 1)\) still has even degree, so it cannot be odd. 5. If the leading term of \(f\) is \(ax^{2n}\), then expanding \(a(x + 1)^{2n}\) produces the nonzero odd-power term \(2na x^{2n-1}\). Lower-degree terms cannot cancel it. Therefore, \(r\) is not even. Thus, \(r\) is neither even nor odd.

Answer

a) Odd; the graph is symmetric about the origin. b) Even; the graph is symmetric about the y-axis. c) Neither even nor odd.
Even and odd functions 111
Find all fourth-degree polynomial functions whose graphs are symmetric about the y-axis and have a local extremum on the x-axis at \(x=2\).

Hints

- Y-axis symmetry means zeros occur in opposite pairs. - A graph that touches the x-axis has a zero of even multiplicity. - Use the degree to determine the multiplicities. - Include a nonzero scale factor to describe the full family.

Solution

1. Y-axis symmetry means the polynomial is even. Therefore, if \(x=2\) is a zero, then \(x=-2\) is also a zero. 2. A local extremum on the x-axis means the graph touches, rather than crosses, the axis. Thus, each zero has even multiplicity. 3. Because the polynomial has degree \(4\), both zeros must have multiplicity \(2\). Therefore, \(f_a(x)=a(x-2)^2(x+2)^2\), where \(a\ne0\). 4. Equivalently, \(f_a(x)=a(x^2-4)^2=ax^4-8ax^2+16a\).

Answer

\(f_a(x)=a(x^2-4)^2\), where \(a\in\mathbb R\setminus\{0\}\)
Even and odd functions 112
Let \(f(x)=(x-5)^3+4(x-5)-2\). Find real numbers \(a\) and \(b\) so that the recentered function \(h(u)=f(u+a)-b\) is odd. Then use your result to identify the center of symmetry of the graph of \(f\).

Hints

- Write the horizontal recentering as a single shift parameter before expanding. - An odd polynomial cannot contain a nonzero even-power term or a nonzero constant term. - Once the recentered function is odd, interpret the horizontal and vertical recentering geometrically.

Solution

1. Let \(t=a-5\). Then \(h(u)=(u+t)^3+4(u+t)-2-b\). 2. Expanding gives \(h(u)=u^3+3tu^2+(3t^2+4)u+(t^3+4t-2-b)\). 3. For \(h\) to be odd, the even-power term and the constant term must be zero. The coefficient of \(u^2\) gives \(3t=0\), so \(t=0\) and therefore \(a=5\). 4. With \(t=0\), the constant term is \(-2-b\). Setting it equal to zero gives \(b=-2\). 5. Thus \(h(u)=u^3+4u\), which is odd. Recentring the graph at \((a,b)=(5,-2)\) produces an odd graph about the origin, so the original graph has center of symmetry \((5, -2)\).

Answer

\(a=5\), \(b=-2\). Then \(h(u)=u^3+4u\) is odd, so the graph of \(f\) has center of symmetry \((5, -2)\).

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