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Antiderivatives and indefinite integrals

Learning goals

  • Finds antiderivatives using basic integration rules.
  • Includes the constant of integration.
  • Distinguishes an indefinite integral from a definite integral.
  • Checks an antiderivative by differentiation.
  • Uses an initial condition to determine a particular constant when given.

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Antiderivatives and indefinite integrals 1
One antiderivative of \(f(x)=3x^2-2\) is \(F(x)=x^3-2x\). Write the complete family of antiderivatives of \(f\). Explain briefly why the family contains an arbitrary constant.

Hints

- Ask what kinds of changes to a function leave its derivative unchanged. - Differentiate the proposed family mentally and see which part disappears.

Solution

1. Any constant can be added to \(F\) without changing its derivative. 2. Therefore every antiderivative has the form \(x^3-2x+C\), where \(C\) is any real constant.

Answer

\(x^3-2x+C\), where \(C\in\mathbb{R}\). The constant is arbitrary because its derivative is \(0\).
Antiderivatives and indefinite integrals 2
Find the indefinite integral \(\int 6x\,\text{d}x\). Why must the answer include \(C\)?

Hints

- Could two different functions have exactly the same derivative? - How could your answer describe all the functions, not just one example?

Solution

1. Reverse the power rule: \(\int6x\,\text{d}x=3x^2+C\). 2. The derivative of any constant is zero, so every value of \(C\) gives an antiderivative of \(6x\).

Answer

\(3x^2+C\), because adding a constant does not change the derivative.
Antiderivatives and indefinite integrals 3
For \(x>0\), is \(F(x)=5\ln(x)\) an antiderivative of \(f(x)=\frac5x\)? Check by differentiating.

Hints

- Which standard derivative rule involves a reciprocal of the input? - How is a fixed coefficient handled when differentiating a function?

Solution

1. Differentiate the proposed function: \(F'(x)=5\cdot\frac1x=\frac5x\). 2. Since \(F'(x)=f(x)\) on \(x>0\), it is an antiderivative.

Answer

Yes. \(F'(x)=\frac5x=f(x)\) for \(x>0\).
Antiderivatives and indefinite integrals 4
A function satisfies \(F'(x)=2x+1\) and \(F(0)=4\). Find \(F(x)\).

Hints

- Can different functions have the stated derivative without having the same value everywhere? - What does the second condition tell you about which of those functions is intended?

Solution

1. An antiderivative of \(2x+1\) is \(F(x)=x^2+x+C\). 2. Since \(F(0)=C=4\), the function is \(F(x)=x^2+x+4\).

Answer

\(F(x)=x^2+x+4\)
Antiderivatives and indefinite integrals 5
A student claims that \(F(x)=\ln(x-3)\) is an antiderivative of \(f(x)=\frac{1}{x-3}\) for every \(x\ne3\). Explain why the claim fails, and correct the formula so it works on both sides of \(3\).

Hints

- What inputs are allowed inside a real logarithm? - How can you keep the logarithm defined on either side of the excluded point without changing the required derivative?

Solution

1. For \(x<3\), the logarithm's input \(x-3\) is negative, so the student's expression is not defined as a real function. 2. The corrected formula is \(F(x)=\ln|x-3|\). It is defined on both \((-\infty,3)\) and \((3,\infty)\), and its derivative is \(\frac{1}{x-3}\) on each interval.

Answer

The formula fails for \(x<3\), where \(x-3\) is negative. A formula that works on both intervals is \(F(x)=\ln|x-3|\), whose derivative is \(\frac{1}{x-3}\) on each interval.
Antiderivatives and indefinite integrals 6
In each case, \(F\) is an antiderivative of \(f\). Find a possible value of \(k\in\mathbb{R}\). a) \(f(x)=7x^6\); \(F(x)=x^k\) b) \(f(x)=kx^3\); \(F(x)=2x^4-5\) c) \(f(x)=\cos(x)\); \(F(x)=\sin(x)+k^2\)

Hints

- What derivative relationship defines an antiderivative? - Use the power rule for differentiation. - What happens to an additive constant when you differentiate? - Match coefficients and exponents after differentiating \(F\).

Solution

1. Because \(F\) is an antiderivative of \(f\), \(F'(x)=f(x)\). 2. For part a, \(F'(x)=kx^{k-1}\). Matching \(7x^6\) gives \(k=7\). 3. For part b, \(F'(x)=8x^3\). Matching \(kx^3\) gives \(k=8\). 4. For part c, \(F'(x)=\cos(x)\) for every real \(k\), because \(k^2\) is constant. Thus, any real value of \(k\) works.

Answer

a) \(k=7\) b) \(k=8\) c) Any \(k\in\mathbb{R}\), such as \(k=0\)
Antiderivatives and indefinite integrals 7
Determine whether \(F\) is an antiderivative of \(f\). a) \(F(x)=\ln(x^2+5)\) and \(f(x)=\frac{2x}{x^2+5}\) b) \(F(x)=\sin(x^2)\) and \(f(x)=2x\cos(x^2)\)

Hints

- What derivative relationship defines an antiderivative? - Which differentiation rule applies to a function inside another function? - Account for the derivative of the inner expression. - Differentiate before comparing the functions.

Solution

1. For part a, differentiate using the chain rule: \(F'(x)=\frac{1}{x^2+5}(2x)=\frac{2x}{x^2+5}=f(x)\). Therefore, \(F\) is an antiderivative of \(f\). 2. For part b, \(F'(x)=\cos(x^2)(2x)=2x\cos(x^2)=f(x)\). Therefore, \(F\) is an antiderivative of \(f\).

Answer

a) Yes, \(F\) is an antiderivative of \(f\). b) Yes, \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 8
Determine whether \(F(x)=\sqrt{2x^2+3}\) is an antiderivative of \(f(x)=\frac{2x}{\sqrt{2x^2+3}}\).

Hints

- What derivative relationship defines an antiderivative? - Differentiate \(F\). - Which rule applies to a square root of a polynomial?

Solution

1. Rewrite \(F(x)=(2x^2+3)^{\frac{1}{2}}\). 2. Differentiate using the chain rule: \(F'(x)=\frac{1}{2}(2x^2+3)^{-\frac{1}{2}}(4x)\). 3. Simplify: \(F'(x)=\frac{2x}{\sqrt{2x^2+3}}=f(x)\). 4. Therefore, \(F\) is an antiderivative of \(f\).

Answer

Yes. Since \(F^{\prime}(x)=\frac{2x}{\sqrt{2x^2+3}}=f(x)\), \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 9
Determine whether \(G(x)=x\sin(x)\) is an antiderivative of \(g(x)=\cos(x)\).

Hints

- Recall the derivative relationship between a function and its antiderivative. - Which rule is needed to differentiate a product? - Compare the entire derivative with \(g\).

Solution

1. Differentiate \(G(x)=x\sin(x)\) using the product rule. 2. \(G'(x)=\sin(x)+x\cos(x)\). 3. Since \(\sin(x)+x\cos(x)\ne\cos(x)\), \(G\) is not an antiderivative of \(g\).

Answer

No. \(G^{\prime}(x)=\sin(x)+x\cos(x)\ne g(x)\).
Antiderivatives and indefinite integrals 10
Let \(f(x)=6\cos(x)-4x\). Give two different antiderivatives \(F_1\) and \(F_2\) of \(f\).

Hints

- Integrate each term separately. - Recall an antiderivative of \(\cos(x)\). - Different constants of integration produce different antiderivatives.

Solution

1. A general antiderivative is \(F(x)=6\sin(x)-2x^2+C\). 2. Choose two different constants, such as \(C=0\) and \(C=5\). This gives \(F_1(x)=6\sin(x)-2x^2\) and \(F_2(x)=6\sin(x)-2x^2+5\).

Answer

\(F_1(x)=6\sin(x)-2x^2\) and \(F_2(x)=6\sin(x)-2x^2+5\)
Antiderivatives and indefinite integrals 11
Determine whether \(F\) is an antiderivative of \(f\). a) \(f(x)=2e^{\frac{1}{2}x+1}\) and \(F(x)=4e^{\frac{1}{2}x+1}-1\) b) \(f(x)=\sin(2x)\) and \(F(x)=\frac{1}{2}\cos(2x)\)

Hints

- What derivative relationship defines an antiderivative? - Apply the chain rule to the linear inner expressions. - Track the sign when differentiating cosine. - Constant terms disappear when differentiated.

Solution

1. For part a, differentiate using the chain rule: \(F'(x)=4e^{\frac{1}{2}x+1}\left(\frac{1}{2}\right)=2e^{\frac{1}{2}x+1}=f(x)\). Thus, \(F\) is an antiderivative of \(f\). 2. For part b, \(F'(x)=\frac{1}{2}[-\sin(2x)](2)=-\sin(2x)\). Since this is not \(f(x)=\sin(2x)\), \(F\) is not an antiderivative of \(f\).

Answer

a) Yes, \(F\) is an antiderivative of \(f\). b) No, \(F\) is not an antiderivative of \(f\).
Antiderivatives and indefinite integrals 12
Let \(f(x)=\frac34x^4-\cos(x)+\pi\). Find \(f^{\prime}(x)\) and one antiderivative \(F(x)\) of \(f\).

Hints

- Track the signs when differentiating and integrating sine and cosine. - Treat \(\pi\) as a constant. - Apply the power rule term by term.

Solution

1. Differentiate term by term: \(f^{\prime}(x)=3x^3+\sin(x)\). 2. Integrate term by term: \(F(x)=\frac{3}{20}x^5-\sin(x)+\pi x\).

Answer

\(f^{\prime}(x)=3x^3+\sin(x)\) \(F(x)=\frac{3}{20}x^5-\sin(x)+\pi x\)
Antiderivatives and indefinite integrals 13
Let \(F(x)=2\cos(x^3)\) and \(f(x)=-6x^2\sin(x^3)\). Show that \(F\) is an antiderivative of \(f\).

Hints

- What equation must hold for \(F\) to be an antiderivative of \(f\)? - Use the chain rule. - Identify the inner and outer functions. - What is the derivative of cosine?

Solution

1. Differentiate \(F\) using the chain rule. 2. The derivative of the outer function \(2\cos(u)\) is \(-2\sin(u)\), and the derivative of the inner function \(u=x^3\) is \(3x^2\). 3. Thus, \(F'(x)=-2\sin(x^3)(3x^2)=-6x^2\sin(x^3)=f(x)\). 4. Therefore, \(F\) is an antiderivative of \(f\).

Answer

\(F^{\prime}(x)=-6x^2\sin(x^3)=f(x)\), so \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 14
Determine whether \(F(x)=\frac{2x^4-3}{x^2}\) is an antiderivative of \(f(x)=4x+6x^{-3}\).

Hints

- What equation must hold for \(F\) to be an antiderivative of \(f\)? - Split the fraction into separate powers before differentiating. - Apply the power rule to negative exponents.

Solution

1. Simplify \(F\): \(F(x)=2x^2-3x^{-2}\). 2. Differentiate using the power rule: \(F'(x)=4x+6x^{-3}\). 3. Since \(F'(x)=f(x)\), \(F\) is an antiderivative of \(f\).

Answer

Yes, \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 15
For \(a\ne0\), consider the family \(h_a(x)=\frac{1}{ax^2}\) for \(x>0\). 1. Find the general form of the antiderivatives \(H_a\). 2. Find the value of \(a\) for which \(H(x)=-\frac{1}{5x}\) is an antiderivative of \(h_a\).

Hints

- Treat \(\frac1a\) as a constant factor. - Rewrite the variable in the denominator using a negative exponent. - Differentiate the given antiderivative and compare coefficients.

Solution

1. Rewrite \(h_a(x)=\frac1a x^{-2}\). Integrating on \(x>0\) gives \(H_a(x)=-\frac{1}{ax}+C\). 2. Differentiate the given function: \(H^{\prime}(x)=\frac{1}{5x^2}\). Comparing this with \(h_a(x)=\frac{1}{ax^2}\) gives \(a=5\).

Answer

1. \(H_a(x)=-\frac{1}{ax}+C\) 2. \(a=5\)
Antiderivatives and indefinite integrals 16
Match each function A–D with its antiderivative 1–4. Justify your choices. A) \(\frac{12}{(x+2)^4}\) B) \(\frac{12}{x^4}\) C) \(-12x^{-5}\) D) \(12(x+2)^{-5}\) 1) \(-\frac{4}{(x+2)^3}\) 2) \(-\frac{4}{x^3}\) 3) \(3x^{-4}\) 4) \(-3(x+2)^{-4}\)

Hints

- Rewrite quotients using negative exponents. - Apply the power rule carefully to the exponent and coefficient. - Differentiate each proposed antiderivative to verify the match.

Solution

1. \(\int12(x+2)^{-4}\,\text{d}x=-4(x+2)^{-3}\), so A matches 1. 2. \(\int12x^{-4}\,\text{d}x=-4x^{-3}\), so B matches 2. 3. \(\int-12x^{-5}\,\text{d}x=3x^{-4}\), so C matches 3. 4. \(\int12(x+2)^{-5}\,\text{d}x=-3(x+2)^{-4}\), so D matches 4.

Answer

A–1; B–2; C–3; D–4
Antiderivatives and indefinite integrals 17
For \(x>0\), find one function whose derivative equals each given expression. a) \(f^{\prime}(x)=\frac32\sqrt{x}\) b) \(g^{\prime}(x)=\frac{2}{3\sqrt[3]{x}}\) c) \(h^{\prime}(x)=\frac{1}{x\sqrt{x}}\)

Hints

- Rewrite radicals and quotients using rational exponents. - Increase the exponent by \(1\), then divide by the new exponent. - Differentiate each result to check it.

Solution

1. Rewrite \(f^{\prime}(x)=\frac32x^{1/2}\). By the power rule, \(f(x)=x^{3/2}\). 2. Rewrite \(g^{\prime}(x)=\frac23x^{-1/3}\). By the power rule, \(g(x)=x^{2/3}\). 3. Rewrite \(h^{\prime}(x)=x^{-3/2}\). By the power rule, \(h(x)=-2x^{-1/2}=-\frac{2}{\sqrt{x}}\).

Answer

a) \(f(x)=x^{3/2}\) b) \(g(x)=x^{2/3}\) c) \(h(x)=-\frac{2}{\sqrt{x}}\)
Antiderivatives and indefinite integrals 18
For \(x>0\), find one function whose derivative equals each expression. a) \(f^{\prime}(x)=\frac45x^{-3/5}\) b) \(g^{\prime}(x)=\frac{3}{4\sqrt[4]{x^3}}-1\)

Hints

- Rewrite radical denominators using negative exponents. - Integrate each term separately. - Differentiate your result to check both the power term and the constant term.

Solution

1. By the power rule, \(f(x)=\frac{4/5}{2/5}x^{2/5}=2x^{2/5}\). 2. Rewrite the first term as \(\frac34x^{-3/4}\). Integrating term by term gives \(g(x)=3x^{1/4}-x\).

Answer

a) \(f(x)=2x^{2/5}\) b) \(g(x)=3\sqrt[4]{x}-x\)
Antiderivatives and indefinite integrals 19
Show that \(F(x)=\frac{1}{3}x^3+2\ln|x|\) is an antiderivative of \(f(x)=x^2+\frac{2}{x}\) for \(x\ne0\).

Hints

- What derivative relationship defines an antiderivative? - Differentiate the sum term by term. - What is the derivative of \(\ln|x|\)? - Keep the constant factors when differentiating.

Solution

1. Differentiate term by term. 2. \(\frac{d}{dx}\left(\frac{1}{3}x^3\right)=x^2\). 3. For \(x\ne0\), \(\frac{d}{dx}[2\ln|x|]=\frac{2}{x}\). 4. Thus, \(F'(x)=x^2+\frac{2}{x}=f(x)\), so \(F\) is an antiderivative of \(f\).

Answer

\(F^{\prime}(x)=x^2+\frac{2}{x}=f(x)\), so \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 20
Let \(f(x)=\frac{2x+e^x}{x^2+e^x}\). Show algebraically that \(F(x)=\ln(x^2+e^x)\) is an antiderivative of \(f\) for every real \(x\).

Hints

- First verify that the expression inside the logarithm is positive. - Differentiate the inner expression separately. - Apply \(\frac{d}{dx}\ln(u)=\frac{u'}{u}\).

Solution

1. Since \(x^2\ge0\) and \(e^x>0\), the expression \(x^2+e^x\) is positive for every real \(x\), so \(F\) is defined on all of \(\mathbb{R}\). 2. Let \(u(x)=x^2+e^x\). Then \(u'(x)=2x+e^x\). 3. By the chain rule, \(F'(x)=\frac{u'(x)}{u(x)}=\frac{2x+e^x}{x^2+e^x}=f(x)\). 4. Therefore, \(F\) is an antiderivative of \(f\) for every real \(x\).

Answer

Yes. Since \(x^2+e^x>0\) and \(F'(x)=\frac{2x+e^x}{x^2+e^x}=f(x)\), \(F\) is an antiderivative on \(\mathbb{R}\).
Antiderivatives and indefinite integrals 21
Let \(f(x)=\frac6x+2\) for \(x>0\). Give two different antiderivatives \(F_1\) and \(F_2\) of \(f\).

Hints

- Recall an antiderivative of \(\frac1x\) on \(x>0\). - Integrate each term separately. - Different constants produce different antiderivatives.

Solution

1. A general antiderivative is \(F(x)=6\ln(x)+2x+C\). 2. Choose two different constants, such as \(C=0\) and \(C=5\). Then \(F_1(x)=6\ln(x)+2x\) and \(F_2(x)=6\ln(x)+2x+5\).

Answer

\(F_1(x)=6\ln(x)+2x\) and \(F_2(x)=6\ln(x)+2x+5\)
Antiderivatives and indefinite integrals 22
For each derivative, find one possible original function and verify your result by differentiating. a) \(f^{\prime}(x)=12x^2\) b) \(f^{\prime}(x)=2x^4\) c) \(f^{\prime}(x)=\frac45x^3\) d) \(f^{\prime}(x)=10\)

Hints

- Reverse the power rule by increasing the exponent by \(1\) and dividing by the new exponent. - Choose each coefficient so that differentiating reproduces the given coefficient. - Differentiate each result to check it.

Solution

1. For a), reverse the power rule: \(f(x)=4x^3\). Check: \(f^{\prime}(x)=12x^2\). 2. For b), \(f(x)=\frac25x^5\). Check: \(f^{\prime}(x)=2x^4\). 3. For c), \(f(x)=\frac15x^4\). Check: \(f^{\prime}(x)=\frac45x^3\). 4. For d), \(f(x)=10x\). Check: \(f^{\prime}(x)=10\).

Answer

a) \(f(x)=4x^3\) b) \(f(x)=\frac25x^5\) c) \(f(x)=\frac15x^4\) d) \(f(x)=10x\)
Antiderivatives and indefinite integrals 23
For each derivative, give one possible original function. a) \(f^{\prime}(x)=5\cos(x)\) b) \(f^{\prime}(x)=-\sin(x)\) c) \(f^{\prime}(x)=\frac{2}{x^2}\) d) \(f^{\prime}(x)=x^2-x\)

Hints

- Recall the derivatives of sine and cosine. - Rewrite expressions with \(x\) in the denominator using negative exponents. - Integrate sums term by term. - Check the sign when working with sine and cosine.

Solution

1. Since the derivative of \(\sin(x)\) is \(\cos(x)\), one choice for a) is \(f(x)=5\sin(x)\). 2. Since the derivative of \(\cos(x)\) is \(-\sin(x)\), one choice for b) is \(f(x)=\cos(x)\). 3. Rewrite \(\frac{2}{x^2}\) as \(2x^{-2}\). Reversing the power rule gives \(f(x)=-2x^{-1}=-\frac2x\). 4. Integrating term by term gives \(f(x)=\frac13x^3-\frac12x^2\).

Answer

a) \(f(x)=5\sin(x)\) b) \(f(x)=\cos(x)\) c) \(f(x)=-\frac2x\) d) \(f(x)=\frac13x^3-\frac12x^2\)
Antiderivatives and indefinite integrals 24
Given \(f^{\prime}(x)=12x^3-5x^4+2\), find one possible function \(f\). Verify your result by differentiating.

Hints

- Apply the reverse power rule to each term. - A constant derivative comes from a linear term. - Differentiate your result to check it.

Solution

1. Integrate each term using the reverse power rule: \(12x^3\) gives \(3x^4\), \(-5x^4\) gives \(-x^5\), and \(2\) gives \(2x\). 2. Thus one possible function is \(f(x)=3x^4-x^5+2x\). 3. Differentiating gives \(f^{\prime}(x)=12x^3-5x^4+2\), as required.

Answer

\(f(x)=3x^4-x^5+2x\). More generally, \(f(x)=3x^4-x^5+2x+C\), where \(C\in\mathbb{R}\).
Antiderivatives and indefinite integrals 25
Given \(g^{\prime}(x)=8\sin(x)+4x^7\), find one possible function \(g\). Verify your result by differentiating.

Hints

- Integrate the two terms separately. - Which trigonometric function has derivative \(\sin(x)\)? Pay attention to the sign. - Reverse the power rule for \(4x^7\). - Differentiate your result to verify it.

Solution

1. Since the derivative of \(-8\cos(x)\) is \(8\sin(x)\), the first term has antiderivative \(-8\cos(x)\). 2. Reversing the power rule gives an antiderivative of \(4x^7\) as \(\frac12x^8\). 3. Therefore, one possible function is \(g(x)=-8\cos(x)+\frac12x^8\). 4. Differentiating gives \(g^{\prime}(x)=8\sin(x)+4x^7\), as required.

Answer

\(g(x)=-8\cos(x)+\frac12x^8\). More generally, \(g(x)=-8\cos(x)+\frac12x^8+C\), where \(C\in\mathbb{R}\).
Antiderivatives and indefinite integrals 26
For \(x\ne0\), find one function \(g\) such that \(g^{\prime}(x)=\cos(x)+\frac{4}{x^5}\).

Hints

- Rewrite the fraction using a negative exponent. - Recall which trigonometric function has derivative \(\cos(x)\). - Reverse the power rule, then differentiate your result to check it.

Solution

1. Rewrite \(\frac{4}{x^5}\) as \(4x^{-5}\). 2. An antiderivative of \(\cos(x)\) is \(\sin(x)\). 3. Reversing the power rule gives an antiderivative of \(4x^{-5}\) as \(-x^{-4}=-\frac1{x^4}\). 4. Therefore, one possible function is \(g(x)=\sin(x)-\frac1{x^4}\).

Answer

\(g(x)=\sin(x)-\frac1{x^4}\) for \(x\ne0\)
Antiderivatives and indefinite integrals 27
Let \(f(x)=6x^2-4x+1\). In each part, find the antiderivative \(F\) whose graph passes through the given point. a) \((0, 7)\) b) \((1, 2)\) c) \((-1, 0)\)

Hints

- Use the power rule in reverse to find the general antiderivative. - A point on the graph gives an equation involving \(C\). - Substitute each point separately.

Solution

1. The general antiderivative is \(F(x)=2x^3-2x^2+x+C\). 2. For part a, \(F(0)=7\) gives \(C=7\). 3. For part b, \(F(1)=2\) gives \(1+C=2\), so \(C=1\). 4. For part c, \(F(-1)=0\) gives \(-2-2-1+C=0\), so \(C=5\).

Answer

a) \(F(x)=2x^3-2x^2+x+7\) b) \(F(x)=2x^3-2x^2+x+1\) c) \(F(x)=2x^3-2x^2+x+5\)
Antiderivatives and indefinite integrals 28
For \(x\ne0\), find one antiderivative \(F\) of each function. a) \(f(x)=x^4-\frac{2}{x^3}+1\) b) \(f(x)=\frac{x^3+5}{x^2}\)

Hints

- Rewrite terms with \(x\) in the denominator using negative exponents. - Split a quotient with a sum in the numerator into separate terms. - Apply the reverse power rule term by term.

Solution

1. For a), rewrite the function as \(x^4-2x^{-3}+1\). Integrating term by term gives \(F(x)=\frac15x^5+x^{-2}+x=\frac15x^5+\frac1{x^2}+x\). 2. For b), simplify first: \(\frac{x^3+5}{x^2}=x+5x^{-2}\). Integrating term by term gives \(F(x)=\frac12x^2-5x^{-1}=\frac12x^2-\frac5x\).

Answer

a) \(F(x)=\frac15x^5+\frac1{x^2}+x\) b) \(F(x)=\frac12x^2-\frac5x\)
Antiderivatives and indefinite integrals 29
For \(x>0\), find one antiderivative \(F\) of each function. a) \(f(x)=3\sqrt{x}-\frac1{\sqrt{x}}\) b) \(f(x)=\frac{\sqrt{x}+2}{\sqrt{x}}\)

Hints

- Rewrite radicals using rational exponents. - Simplify the quotient in b) before integrating. - Apply the reverse power rule carefully to fractional exponents.

Solution

1. For a), rewrite the function as \(3x^{1/2}-x^{-1/2}\). Integrating term by term gives \(F(x)=2x^{3/2}-2x^{1/2}=2x^{3/2}-2\sqrt{x}\). 2. For b), simplify first: \(\frac{\sqrt{x}+2}{\sqrt{x}}=1+2x^{-1/2}\). Integrating gives \(F(x)=x+4x^{1/2}=x+4\sqrt{x}\).

Answer

a) \(F(x)=2x^{3/2}-2\sqrt{x}\) b) \(F(x)=x+4\sqrt{x}\)
Antiderivatives and indefinite integrals 30
Let \(f(x)=8x^3-6x^2+5\). Give three different antiderivatives \(F_1\), \(F_2\), and \(F_3\) of \(f\).

Hints

- First find the general antiderivative. - All antiderivatives of the same function differ by a constant. - Choose three different values for that constant.

Solution

1. Integrating term by term gives the general antiderivative \(F(x)=2x^4-2x^3+5x+C\). 2. Choose three different constants, such as \(C=0\), \(C=3\), and \(C=-1\). 3. This gives \(F_1(x)=2x^4-2x^3+5x\), \(F_2(x)=2x^4-2x^3+5x+3\), and \(F_3(x)=2x^4-2x^3+5x-1\).

Answer

\(F_1(x)=2x^4-2x^3+5x\) \(F_2(x)=2x^4-2x^3+5x+3\) \(F_3(x)=2x^4-2x^3+5x-1\)
Antiderivatives and indefinite integrals 31
Find three antiderivatives \(F_1\), \(F_2\), and \(F_3\) of \(f(x)=3x^2+4x\) that satisfy these conditions: 1. \(F_1(0)=0\) 2. \(F_2(0)=10\) 3. \(F_3(1)=5\)

Hints

- First write the general antiderivative with a constant \(C\). - Substitute the given input and output values. - Solve each resulting equation for its constant.

Solution

1. The general antiderivative is \(F(x)=x^3+2x^2+C\). 2. From \(F_1(0)=0\), \(C_1=0\), so \(F_1(x)=x^3+2x^2\). 3. From \(F_2(0)=10\), \(C_2=10\), so \(F_2(x)=x^3+2x^2+10\). 4. From \(F_3(1)=5\), \(1+2+C_3=5\), so \(C_3=2\) and \(F_3(x)=x^3+2x^2+2\).

Answer

1. \(F_1(x)=x^3+2x^2\) 2. \(F_2(x)=x^3+2x^2+10\) 3. \(F_3(x)=x^3+2x^2+2\)
Antiderivatives and indefinite integrals 32
Find one antiderivative \(F\) of \(f(x)=\frac12(x^2-3)^2\).

Hints

- Expand the squared binomial before integrating. - Integrate each term of the resulting polynomial separately. - Use the reverse power rule.

Solution

1. Expand the square: \(f(x)=\frac12x^4-3x^2+\frac92\). 2. Integrate term by term to obtain \(F(x)=\frac1{10}x^5-x^3+\frac92x\). 3. Differentiating this expression reproduces \(f(x)\).

Answer

\(F(x)=\frac1{10}x^5-x^3+\frac92x\)
Antiderivatives and indefinite integrals 33
Find one antiderivative \(F\) of each function. a) \(f(x)=5\sin(x)+x^4\) b) \(f(x)=\frac3{x^2}-2\cos(x)\), for \(x\ne0\) c) \(f(x)=4\left(\cos(x)+\frac1{\sqrt{x}}\right)\), for \(x>0\)

Hints

- Recall the antiderivatives of sine and cosine. - Rewrite reciprocal powers and radicals using exponents. - Integrate each term separately and keep constant factors.

Solution

1. For a), integrate term by term: \(F(x)=-5\cos(x)+\frac15x^5\). 2. For b), rewrite \(\frac3{x^2}\) as \(3x^{-2}\). Integrating gives \(F(x)=-\frac3x-2\sin(x)\). 3. For c), integrate inside the parentheses and retain the factor \(4\): \(F(x)=4\sin(x)+8\sqrt{x}\).

Answer

a) \(F(x)=-5\cos(x)+\frac15x^5\) b) \(F(x)=-\frac3x-2\sin(x)\) c) \(F(x)=4\sin(x)+8\sqrt{x}\)
Antiderivatives and indefinite integrals 34
Let \(f(x)=\sin(x)-4x^3\). Find the antiderivative \(F\) whose graph passes through \((0, 2)\).

Hints

- First find the general antiderivative with a constant \(C\). - Substitute the coordinates of the given point. - Use \(\cos(0)=1\) to solve for \(C\).

Solution

1. The general antiderivative is \(F(x)=-\cos(x)-x^4+C\). 2. Use the condition \(F(0)=2\): \(-\cos(0)+C=2\). 3. Since \(\cos(0)=1\), \(-1+C=2\), so \(C=3\). 4. Therefore, \(F(x)=-\cos(x)-x^4+3\).

Answer

\(F(x)=-\cos(x)-x^4+3\)
Antiderivatives and indefinite integrals 35
Find the antiderivative \(F\) of \(f(x)=\frac{1}{2}x^3-3x^2+5\) that has a zero at \(x=2\).

Hints

- Integrate each polynomial term using the power rule. - What equation follows from a zero at \(x=2\)? - Include the integration constant in the general antiderivative. - Solve the resulting equation for \(C\).

Solution

1. The general antiderivative is \(F(x)=\frac{1}{8}x^4-x^3+5x+C\). 2. The zero at \(x=2\) means \(F(2)=0\): \(2-8+10+C=0\). 3. Therefore, \(4+C=0\), so \(C=-4\). 4. Thus, \(F(x)=\frac{1}{8}x^4-x^3+5x-4\).

Answer

\(F(x)=\frac{1}{8}x^4-x^3+5x-4\)
Antiderivatives and indefinite integrals 36
Let \(f(x)=\frac{4}{x^3}+\frac{1}{2}\) for \(x>0\). Find the antiderivative \(F\) that satisfies \(F(2)=0\).

Hints

- Rewrite the reciprocal term using a negative exponent. - Apply the power rule for antiderivatives carefully. - Use the condition \(F(2)=0\). - Solve for the remaining constant.

Solution

1. Rewrite \(f(x)=4x^{-3}+\frac{1}{2}\). 2. Integrate: \(F(x)=-2x^{-2}+\frac{1}{2}x+C=-\frac{2}{x^2}+\frac{1}{2}x+C\). 3. Use \(F(2)=0\): \(-\frac{2}{4}+1+C=0\). 4. Thus, \(\frac{1}{2}+C=0\), so \(C=-\frac{1}{2}\). 5. Therefore, \(F(x)=-\frac{2}{x^2}+\frac{1}{2}x-\frac{1}{2}\).

Answer

\(F(x)=-\frac{2}{x^2}+\frac{1}{2}x-\frac{1}{2}\)
Antiderivatives and indefinite integrals 37
Let \(f(x)=4x^3-6x\). a) Determine algebraically whether \(F(x)=x^4-3x^2+5\) is an antiderivative of \(f\). b) State the definition of an antiderivative and use it to explain why \(H(x)=x^4-3x^2-12\) is also an antiderivative of \(f\).

Hints

- Differentiate the proposed antiderivative. - What must the derivative of an antiderivative equal? - What effect does an additive constant have on a derivative?

Solution

1. Differentiate \(F\): \(F'(x)=4x^3-6x=f(x)\). Thus, \(F\) is an antiderivative of \(f\). 2. A function is an antiderivative of \(f\) on an interval when its derivative equals \(f\) at every point of the interval. 3. Differentiate \(H\): \(H'(x)=4x^3-6x=f(x)\). The different constant term has no effect on the derivative. 4. Therefore, \(H\) is also an antiderivative of \(f\).

Answer

a) Yes, because \(F'(x)=4x^3-6x=f(x)\). b) An antiderivative has derivative \(f\). Since \(H'(x)=4x^3-6x=f(x)\), \(H\) is also an antiderivative.
Antiderivatives and indefinite integrals 38
For \(x>0\), let \(f(x)=\frac{1}{2\sqrt{x}}+e^x\). Find the antiderivative \(F\) that satisfies \(F(1)=e+4\).

Hints

- Recall the antiderivatives related to square-root and exponential functions. - Substitute the given input into the general antiderivative. - Solve the resulting equation for \(C\).

Solution

1. The general antiderivative is \(F(x)=\sqrt{x}+e^x+C\). 2. Apply \(F(1)=e+4\): \(1+e+C=e+4\). 3. Therefore, \(C=3\). 4. Thus, \(F(x)=\sqrt{x}+e^x+3\).

Answer

\(F(x)=\sqrt{x}+e^x+3\)
Antiderivatives and indefinite integrals 39
Find one antiderivative \(F\) of each function. a) \(f(x)=4e^{2x}\) b) \(f(x)=e^{5-x}+x^2\) c) \(f(x)=\frac12e^{4x-2}-3\)

Hints

- For \(e^{ax+b}\), divide by the derivative of the exponent. - Integrate sums term by term. - Differentiate each result to check the inner-factor adjustment.

Solution

1. For a), account for the inner derivative \(2\): \(F(x)=2e^{2x}\). 2. For b), the inner derivative of \(5-x\) is \(-1\), so an antiderivative of \(e^{5-x}\) is \(-e^{5-x}\). Therefore, \(F(x)=-e^{5-x}+\frac13x^3\). 3. For c), account for the inner derivative \(4\): \(F(x)=\frac18e^{4x-2}-3x\).

Answer

a) \(F(x)=2e^{2x}\) b) \(F(x)=-e^{5-x}+\frac13x^3\) c) \(F(x)=\frac18e^{4x-2}-3x\)
Antiderivatives and indefinite integrals 40
Let \(f(x)=3e^{-x}+2\). Find the antiderivative \(F\) whose graph passes through \((0, 1)\).

Hints

- First find the general antiderivative with a constant \(C\). - Account for the inner derivative of \(-x\). - Substitute the coordinates of the given point to determine \(C\).

Solution

1. Accounting for the inner derivative \(-1\), the general antiderivative is \(F(x)=-3e^{-x}+2x+C\). 2. Use \(F(0)=1\): \(-3e^0+C=1\). 3. Since \(e^0=1\), \(-3+C=1\), so \(C=4\). 4. Therefore, \(F(x)=-3e^{-x}+2x+4\).

Answer

\(F(x)=-3e^{-x}+2x+4\)
Antiderivatives and indefinite integrals 41
Let \(f(x)=\frac{1}{x^2}+1\) for \(x>0\). a) Give four different antiderivatives of \(f\). b) Find the antiderivative \(F\) whose graph passes through \((1, 0)\).

Hints

- Use the power rule for antiderivatives. - What effect does an additive constant have on the derivative? - A point on the graph gives an equation for \(C\). - Substitute \(x=1\) and the given output.

Solution

1. Rewrite \(f(x)=x^{-2}+1\). The family of antiderivatives is \(F(x)=-\frac{1}{x}+x+C\). 2. Four examples are obtained by choosing different constants, such as \(C=0, 1, -5, 10\). 3. For part b, use \(F(1)=0\): \(-1+1+C=0\), so \(C=0\). 4. Therefore, the required antiderivative is \(F(x)=-\frac{1}{x}+x\).

Answer

a) Examples: \(F_1(x)=-\frac{1}{x}+x\), \(F_2(x)=-\frac{1}{x}+x+1\), \(F_3(x)=-\frac{1}{x}+x-5\), and \(F_4(x)=-\frac{1}{x}+x+10\) b) \(F(x)=-\frac{1}{x}+x\)
Antiderivatives and indefinite integrals 42
The graphs of two functions \(p\) and \(q\) are shown. Could they be antiderivatives of the same function? Justify your answer and find \(q(x)-p(x)\).
Figure for problem 562580

Hints

- Compare the vertical separation of the curves at several x-values. - What happens to a derivative when a constant is added to a function?

Solution

1. At \(x=0\), the graph gives \(p(0)=0\) and \(q(0)=3\). The same vertical gap appears throughout the displayed interval. 2. Thus \(q(x)=p(x)+3\), so \(q'(x)=p'(x)\). They can be antiderivatives of the same function. 3. Their difference is \(q(x)-p(x)=3\) across the displayed interval.

Answer

Yes. The graphs are vertical shifts: \(q(x)-p(x)=3\). Thus \(q'(x)=p'(x)\).
Antiderivatives and indefinite integrals 43
A skateboarder's acceleration is \(a(t)=6t\) meters per second squared, with \(t\) in seconds. At \(t=0\), the skateboarder has velocity \(3\,\text{m/s}\). Find the velocity function \(v(t)\) by antidifferentiating, then find \(v(2)\).

Hints

- Velocity is an antiderivative of acceleration. - Use the starting velocity to determine the integration constant. - Substitute the requested time only after finding the velocity formula.

Solution

1. Since \(v'(t)=a(t)=6t\), an antiderivative is \(v(t)=3t^2+C\). 2. The initial velocity gives \(v(0)=C=3\), so \(v(t)=3t^2+3\). 3. Then \(v(2)=3\cdot4+3=15\,\text{m/s}\).

Answer

\(v(t)=3t^2+3\) meters per second and \(v(2)=15\,\text{m/s}\)
Antiderivatives and indefinite integrals 44
Match each function \(f_1\) through \(f_4\) with its antiderivative \(F_A\) through \(F_D\). 1. \(f_1(x)=4\cos(4x-2)\) 2. \(f_2(x)=\frac{2x+1}{x^2+x}\) 3. \(f_3(x)=(2x-3)^4\) 4. \(f_4(x)=e^{0.5x}\) A. \(F_A(x)=\ln|x^2+x|+5\) B. \(F_B(x)=2e^{0.5x}-1\) C. \(F_C(x)=\sin(4x-2)\) D. \(F_D(x)=\frac{1}{10}(2x-3)^5+2\)

Hints

- Use the chain rule to differentiate the candidate antiderivatives. - Look for a numerator that is the derivative of the denominator. - For a linear inner function, account for its constant derivative. - Differentiate each candidate to check your matches.

Solution

1. Differentiate \(F_C\): \(F_C'(x)=4\cos(4x-2)=f_1(x)\). Thus \(f_1\) matches \(F_C\). 2. Since the derivative of \(x^2+x\) is \(2x+1\), \(\frac{d}{dx}\ln|x^2+x|=\frac{2x+1}{x^2+x}=f_2(x)\). Thus \(f_2\) matches \(F_A\). 3. Differentiate \(F_D\): \(F_D'(x)=\frac{1}{10}\cdot 5(2x-3)^4\cdot 2=(2x-3)^4=f_3(x)\). Thus \(f_3\) matches \(F_D\). 4. Differentiate \(F_B\): \(F_B'(x)=2\cdot 0.5e^{0.5x}=e^{0.5x}=f_4(x)\). Thus \(f_4\) matches \(F_B\).

Answer

1. C 2. A 3. D 4. B
Antiderivatives and indefinite integrals 45
Find one antiderivative of each function. Treat every symbol other than the function variable as a constant. Assume \(a>0\), \(k\ne0\), and \(x>0\) whenever those symbols are parameters. a) \(f(x)=\frac{4}{k}x^3-3ax^2\) b) \(g(t)=\frac{k}{t^2}+a\) c) \(h(a)=\frac{a}{x}+\sqrt{x}\)

Hints

- Identify the function variable in each part. - Treat all other symbols as constants. - Rewrite a variable in the denominator using a negative exponent before applying the power rule. - Differentiate your result to check it.

Solution

1. Integrate with respect to \(x\): \(F(x)=\frac{4}{k}\cdot\frac{x^4}{4}-3a\cdot\frac{x^3}{3}=\frac{x^4}{k}-ax^3\). 2. Rewrite \(\frac{k}{t^2}=kt^{-2}\) and integrate with respect to \(t\): \(G(t)=-kt^{-1}+at=-\frac{k}{t}+at\). 3. Integrate with respect to \(a\), treating \(x\) as a constant: \(H(a)=\frac1x\cdot\frac{a^2}{2}+a\sqrt{x}=\frac{a^2}{2x}+a\sqrt{x}\).

Answer

a) \(F(x)=\frac{x^4}{k}-ax^3\) b) \(G(t)=-\frac{k}{t}+at\) c) \(H(a)=\frac{a^2}{2x}+a\sqrt{x}\)
Antiderivatives and indefinite integrals 46
Find one antiderivative of each function. Treat \(a\), \(k\), and \(x\) as constants whenever they are not the function variable. Assume \(k\ne0\) in part a and \(z\ge0\) in part c. a) \(f(x)=-\frac1k\sin(x)+k^2\) b) \(g(t)=e^t-k^2t\) c) \(h(z)=z^{3/2}+\frac52a^2\)

Hints

- Check the sign when integrating \(-\sin(x)\). - The exponential function \(e^t\) is its own antiderivative. - Apply the power rule to fractional exponents. - Differentiate each result to verify it.

Solution

1. Integrate with respect to \(x\): \(F(x)=\frac1k\cos(x)+k^2x\). 2. Integrate with respect to \(t\): \(G(t)=e^t-\frac12k^2t^2\). 3. Apply the power rule with respect to \(z\): \(H(z)=\frac25z^{5/2}+\frac52a^2z\).

Answer

a) \(F(x)=\frac1k\cos(x)+k^2x\) b) \(G(t)=e^t-\frac12k^2t^2\) c) \(H(z)=\frac25z^{5/2}+\frac52a^2z\)
Antiderivatives and indefinite integrals 47
Let \(f(x) = e^{2x} + \frac{1}{x+2}\) for \(x>-2\). Find the antiderivative \(F\) of \(f\) whose graph passes through \((0, 1.5)\).

Hints

- Which integration rules apply to the two terms? - What equation follows from the point on the graph? - How can you use that equation to find \(C\)? - Keep the logarithm's domain in mind.

Solution

1. Integrate each term: \(F(x)=\frac{1}{2}e^{2x}+\ln(x+2)+C\). The domain condition \(x>-2\) makes \(x+2>0\). 2. Use \(F(0)=1.5\): \(\frac{1}{2}+\ln(2)+C=1.5\). 3. Solve for the constant: \(C=1-\ln(2)\). 4. Therefore, \(F(x)=\frac{1}{2}e^{2x}+\ln(x+2)+1-\ln(2)\).

Answer

\(F(x)=\frac{1}{2}e^{2x}+\ln(x+2)+1-\ln(2)\)
Antiderivatives and indefinite integrals 48
Let \(g(x)=6\sin(3x+2)\). Find all antiderivatives \(G\) of \(g\) that take both positive and negative values.

Hints

- First find the general antiderivative of \(g\). - Determine the range of the cosine term. - What must be true of the minimum and maximum for the function to have both signs? - Solve the resulting inequalities for \(C\).

Solution

1. The general antiderivative is \(G(x)=-2\cos(3x+2)+C\). 2. Because cosine ranges from \(-1\) to \(1\), the term \(-2\cos(3x+2)\) ranges from \(-2\) to \(2\). Thus the range of \(G\) is \([C-2, C+2]\). 3. For \(G\) to take both positive and negative values, its minimum must be below \(0\) and its maximum above \(0\): \(C-2<0\) and \(C+2>0\). 4. These inequalities give \(-2<C<2\).

Answer

\(G(x)=-2\cos(3x+2)+C\), where \(C\in(-2, 2)\)
Antiderivatives and indefinite integrals 49
Find an antiderivative \(F\) of \(f(x)=\frac{1}{2}x^3-e^{2-x}\) that satisfies \(F(2)=10\).

Hints

- Find an antiderivative of each term separately. - Check the sign that comes from the derivative of \(2-x\). - Use the given value to solve for the integration constant. - Differentiate your result to verify it.

Solution

1. Integrate each term: \(F(x)=\frac{1}{8}x^4+e^{2-x}+C\). 2. Apply \(F(2)=10\): \(\frac{1}{8}(2)^4+e^0+C=10\). 3. Simplify: \(2+1+C=10\), so \(C=7\). 4. Therefore, \(F(x)=\frac{1}{8}x^4+e^{2-x}+7\).

Answer

\(F(x)=\frac{1}{8}x^4+e^{2-x}+7\)
Antiderivatives and indefinite integrals 50
Find an antiderivative \(F\) of \(f(x)=\frac{2}{x+3}-\cos\left(\frac{x}{2}\right)\) for \(x>-3\) that satisfies \(F(0)=0\).

Hints

- Which function has a derivative of the form \(\frac{1}{x+a}\)? - Account for the linear inner function when integrating the cosine term. - Use \(F(0)=0\) to isolate \(C\). - A logarithm property can combine the two logarithmic terms.

Solution

1. Integrate each term: \(F(x)=2\ln(x+3)-2\sin\left(\frac{x}{2}\right)+C\). The domain condition ensures \(x+3>0\). 2. Apply \(F(0)=0\): \(2\ln(3)-2\sin(0)+C=0\). 3. Therefore, \(C=-2\ln(3)\). 4. The required antiderivative is \(F(x)=2\ln(x+3)-2\sin\left(\frac{x}{2}\right)-2\ln(3)\).

Answer

\(F(x)=2\ln(x+3)-2\sin\left(\frac{x}{2}\right)-2\ln(3)\), equivalently \(F(x)=2\ln\left(\frac{x+3}{3}\right)-2\sin\left(\frac{x}{2}\right)\)
Antiderivatives and indefinite integrals 51
Let \(f(x)=2e^{3x+3}-4x\). Find the antiderivative \(F\) of \(f\) that satisfies \(F(-1)=5\).

Hints

- Integrate the exponential and polynomial terms separately. - How does the derivative of \(3x+3\) affect the exponential antiderivative? - Substitute the given input and output to find \(C\). - Solve the resulting equation for the unknown constant.

Solution

1. Integrate term by term: \(F(x)=\frac{2}{3}e^{3x+3}-2x^2+C\). 2. Apply \(F(-1)=5\): \(\frac{2}{3}e^0-2(-1)^2+C=5\). 3. Simplify: \(\frac{2}{3}-2+C=5\), so \(-\frac{4}{3}+C=5\). 4. Thus, \(C=\frac{19}{3}\), and \(F(x)=\frac{2}{3}e^{3x+3}-2x^2+\frac{19}{3}\).

Answer

\(F(x)=\frac{2}{3}e^{3x+3}-2x^2+\frac{19}{3}\)
Antiderivatives and indefinite integrals 52
Let \(f(x)=x^2-5\) and \(g(x)=\frac{1}{3}x+2\). a) Show that \(H(x)=\left(\frac{1}{3}x+2\right)^3-5x\) is an antiderivative of \(h(x)=f(g(x))\). b) Find the antiderivative \(K\) of \(k(x)=6g(f(x))\) that satisfies \(K(3)=20\).

Hints

- How do you differentiate a composite function? - What equation must hold for one function to be an antiderivative of another? - Compose the functions before integrating. - How does a specified function value determine the integration constant?

Solution

1. For part a, compose the functions: \(h(x)=f(g(x))=\left(\frac{1}{3}x+2\right)^2-5\). 2. Differentiate \(H\): \(H'(x)=3\left(\frac{1}{3}x+2\right)^2\left(\frac{1}{3}\right)-5=\left(\frac{1}{3}x+2\right)^2-5=h(x)\). Therefore, \(H\) is an antiderivative of \(h\). 3. For part b, \(k(x)=6g(f(x))=6\left(\frac{1}{3}(x^2-5)+2\right)=2x^2+2\). 4. The general antiderivative is \(K(x)=\frac{2}{3}x^3+2x+C\). 5. Use \(K(3)=20\): \(\frac{2}{3}(3)^3+2\cdot 3+C=20\), so \(24+C=20\) and \(C=-4\). 6. Thus, \(K(x)=\frac{2}{3}x^3+2x-4\).

Answer

a) \(H'(x)=\left(\frac{1}{3}x+2\right)^2-5=f(g(x))\), so \(H\) is an antiderivative of \(h\). b) \(K(x)=\frac{2}{3}x^3+2x-4\)
Antiderivatives and indefinite integrals 53
Find the value of \(a\) that makes \(F\) an antiderivative of \(f\). a) \(f(x)=\frac{1}{3}x^2\); \(F(x)=ax^3\) b) \(f(x)=(a-1)x^{a-2}\); \(F(x)=x^4\) c) \(f(x)=e^{3x}\); \(F(x)=ae^{3x}+10\)

Hints

- Use the condition \(F'(x)=f(x)\). - Pay close attention to the chain rule in part c. - In part b, compare exponents first. - Also verify that the coefficients match.

Solution

1. In each part, require \(F'(x)=f(x)\). 2. For part a, \(F'(x)=3ax^2\). Matching coefficients with \(\frac{1}{3}x^2\) gives \(3a=\frac{1}{3}\), so \(a=\frac{1}{9}\). 3. For part b, \(F'(x)=4x^3\). Matching exponents gives \(a-2=3\), so \(a=5\). Then \(a-1=4\), so the coefficient also matches. 4. For part c, \(F'(x)=3ae^{3x}\). Matching coefficients with \(e^{3x}\) gives \(3a=1\), so \(a=\frac{1}{3}\).

Answer

a) \(a=\frac{1}{9}\) b) \(a=5\) c) \(a=\frac{1}{3}\)
Antiderivatives and indefinite integrals 54
Decide whether each statement “\(F\) is an antiderivative of \(f\)” is true or false. Justify your answer by differentiating. a) \(F(x)=(x-1)e^x\) and \(f(x)=xe^x\) b) \(F(x)=\frac{1}{x^2+1}\) and \(f(x)=\frac{2x}{(x^2+1)^2}\)

Hints

- Which differentiation rule applies to the product in part a? - Rewrite the fraction in part b using a negative exponent. - Track the negative sign and the derivative of the inner expression.

Solution

1. For part a, use the product rule: \(F'(x)=e^x+(x-1)e^x=xe^x=f(x)\). The statement is true. 2. For part b, write \(F(x)=(x^2+1)^{-1}\). Then \(F'(x)=-(x^2+1)^{-2}(2x)=-\frac{2x}{(x^2+1)^2}\), which is not equal to \(f(x)\). The statement is false.

Answer

a) True, because \(F'(x)=xe^x=f(x)\). b) False, because \(F'(x)=-\frac{2x}{(x^2+1)^2}\ne f(x)\).
Antiderivatives and indefinite integrals 55
Match each function \(f\) with its antiderivative \(F\). For each function with no match, give any antiderivative. Antiderivatives: 1. \(F(x)=x^2+3x-5\) 2. \(F(x)=2x^3+7\) 3. \(F(x)=x^4-\frac{1}{2}x^2+10\) 4. \(F(x)=x^5-1\) Functions: A. \(f(x)=6x^2\) B. \(f(x)=2x+3\) C. \(f(x)=\frac{1}{2}x^3\) D. \(f(x)=4x^3-x\) E. \(f(x)=5x^4\) F. \(f(x)=3\)

Hints

- Differentiate each proposed antiderivative. - Use the power rule in reverse for functions that have no match. - An antiderivative \(F\) must satisfy \(F'=f\). - You may choose any additive constant when none is specified.

Solution

1. Differentiate the listed antiderivatives: \(F_1'(x)=2x+3\), \(F_2'(x)=6x^2\), \(F_3'(x)=4x^3-x\), and \(F_4'(x)=5x^4\). 2. Therefore, the matches are A-2, B-1, D-3, and E-4. 3. For C, one antiderivative is \(\int \frac{1}{2}x^3\,\text{d}x=\frac{1}{8}x^4\). 4. For F, one antiderivative is \(\int 3\,\text{d}x=3x\).

Answer

Matches: A-2, B-1, D-3, E-4. For C: \(F(x)=\frac{1}{8}x^4\) For F: \(F(x)=3x\)
Antiderivatives and indefinite integrals 56
The functions \(g_1\) through \(g_4\) and two antiderivatives \(G_A\) and \(G_B\) are given: \(g_1(x)=4x-1\) \(g_2(x)=3x^2-4x\) \(g_3(x)=x^3\) \(g_4(x)=2x^3-\frac{1}{2}x^2\) \(G_A(x)=2x^2-x+4\) \(G_B(x)=\frac{1}{2}x^4-\frac{1}{6}x^3-1\) a) Match \(G_A\) and \(G_B\) with the appropriate functions \(g_i\). Briefly justify each match. b) For each remaining function, find the antiderivative whose graph passes through \((1, 2)\).

Hints

- How are derivatives and antiderivatives related? - First write each general antiderivative with a constant \(C\). - Substitute the coordinates of the given point to determine \(C\).

Solution

1. For part a, \(G_A'(x)=4x-1=g_1(x)\), and \(G_B'(x)=2x^3-\frac{1}{2}x^2=g_4(x)\). 2. For \(g_2(x)=3x^2-4x\), the general antiderivative is \(G_2(x)=x^3-2x^2+C\). Using \(G_2(1)=2\) gives \(-1+C=2\), so \(C=3\). Thus, \(G_2(x)=x^3-2x^2+3\). 3. For \(g_3(x)=x^3\), the general antiderivative is \(G_3(x)=\frac{1}{4}x^4+C\). Using \(G_3(1)=2\) gives \(\frac{1}{4}+C=2\), so \(C=\frac{7}{4}\). Thus, \(G_3(x)=\frac{1}{4}x^4+\frac{7}{4}\).

Answer

a) \(G_A\) matches \(g_1\), and \(G_B\) matches \(g_4\). b) \(G_2(x)=x^3-2x^2+3\); \(G_3(x)=\frac{1}{4}x^4+\frac{7}{4}\)
Antiderivatives and indefinite integrals 57
Let \(f(x)=x^2-4x+5\). a) Find the slope of the graph of an antiderivative \(F\) of \(f\) at \((1, F(1))\). b) Is there another point \(S\) on the graph of \(F\) where the tangent line is parallel to the tangent line at \((1, F(1))\)? Justify your answer and, if it exists, give the x-coordinate of \(S\). c) Find the antiderivative \(G\) of \(f\) whose graph passes through \((3, 8)\).

Hints

- How is the slope of \(F\) related to \(f\)? - When are two tangent lines parallel? - What equation gives all points with the same slope? - Use the given point to determine \(C\).

Solution

1. The slope of \(F\) at \(x=1\) is \(F'(1)=f(1)=1-4+5=2\). 2. Parallel tangent lines have equal slopes, so solve \(f(x)=2\): \(x^2-4x+5=2\). 3. This becomes \(x^2-4x+3=0\), or \((x-1)(x-3)=0\). Besides \(x=1\), the other solution is \(x=3\). 4. For part c, the general antiderivative is \(G(x)=\frac{1}{3}x^3-2x^2+5x+C\). 5. Apply \(G(3)=8\): \(9-18+15+C=8\), so \(6+C=8\) and \(C=2\). 6. Therefore, \(G(x)=\frac{1}{3}x^3-2x^2+5x+2\).

Answer

a) \(2\) b) Yes. The other point has x-coordinate \(x=3\). c) \(G(x)=\frac{1}{3}x^3-2x^2+5x+2\)
Antiderivatives and indefinite integrals 58
Let \(g(x)=\frac{3\sin(x)-2}{5}\). a) Find one antiderivative \(G_1\) of \(g\). b) Find another antiderivative \(G_2\) whose graph passes through \(P(0, 1)\).

Hints

- Split the fraction into separate terms. - Check the sign when integrating \(\sin(x)\). - Use the given point to determine the constant of integration.

Solution

1. Rewrite \(g(x)=\frac35\sin(x)-\frac25\). A general antiderivative is \(G(x)=-\frac35\cos(x)-\frac25x+C\). 2. For part a, choose \(C=0\): \(G_1(x)=-\frac35\cos(x)-\frac25x\). 3. For part b, use \(G_2(0)=1\): \(-\frac35+C=1\), so \(C=\frac85\). Therefore, \(G_2(x)=-\frac35\cos(x)-\frac25x+\frac85\).

Answer

a) \(G_1(x)=-\frac35\cos(x)-\frac25x\) b) \(G_2(x)=-\frac35\cos(x)-\frac25x+\frac85\)
Antiderivatives and indefinite integrals 59
Show that \(f(x)=(x^3-4x)e^x+5\) is an antiderivative of \(g(x)=(x^3+3x^2-4x-4)e^x\).

Hints

- What equation must hold for \(f\) to be an antiderivative of \(g\)? - Use the product rule on the nonconstant term. - What happens to the constant \(5\) when differentiated? - Factor out the common exponential term after differentiating.

Solution

1. Differentiate the product \((x^3-4x)e^x\) using the product rule. The constant \(5\) differentiates to \(0\). 2. \(f'(x)=(3x^2-4)e^x+(x^3-4x)e^x\). 3. Factor out \(e^x\): \(f'(x)=(x^3+3x^2-4x-4)e^x\). 4. This equals \(g(x)\), so \(f\) is an antiderivative of \(g\).

Answer

\(f^{\prime}(x)=(3x^2-4)e^x+(x^3-4x)e^x=(x^3+3x^2-4x-4)e^x=g(x)\). Therefore, \(f\) is an antiderivative of \(g\).
Antiderivatives and indefinite integrals 60
Let \(f(x)=(x^2-2)\cos(x)-2x\sin(x)\) and \(g(x)=-x^2\sin(x)\). Show that \(f\) is an antiderivative of \(g\).

Hints

- What derivative relationship defines an antiderivative? - Apply the product rule separately to the two products. - Track the signs of the trigonometric derivatives carefully. - Look for terms that cancel after differentiation.

Solution

1. Differentiate both terms of \(f\) using the product rule. 2. The derivative of \((x^2-2)\cos(x)\) is \(2x\cos(x)-(x^2-2)\sin(x)\). 3. The derivative of \(-2x\sin(x)\) is \(-2\sin(x)-2x\cos(x)\). 4. Combine the results: \(f'(x)=2x\cos(x)-(x^2-2)\sin(x)-2\sin(x)-2x\cos(x)\). 5. The cosine terms cancel, and \(2\sin(x)-2\sin(x)=0\), leaving \(f'(x)=-x^2\sin(x)=g(x)\). 6. Therefore, \(f\) is an antiderivative of \(g\).

Answer

\(f^{\prime}(x)=2x\cos(x)-(x^2-2)\sin(x)-2\sin(x)-2x\cos(x)=-x^2\sin(x)=g(x)\). Therefore, \(f\) is an antiderivative of \(g\).
Antiderivatives and indefinite integrals 61
Let \(f(x)=3x^2\sin(x)+x^3\cos(x)\). Find one antiderivative \(F\) of \(f\).

Hints

- Does the expression resemble the result of a familiar differentiation rule? - Look for two terms that could come from differentiating a product. - Find functions \(u\) and \(v\) whose product has derivative \(f\). - Differentiate your proposed antiderivative to check it.

Solution

1. Recognize the product-rule pattern \(u'v+uv'\). 2. Choose \(u(x)=x^3\) and \(v(x)=\sin(x)\). Then \(u'(x)=3x^2\) and \(v'(x)=\cos(x)\). 3. Therefore, \(\frac{d}{dx}[x^3\sin(x)]=3x^2\sin(x)+x^3\cos(x)=f(x)\). 4. One antiderivative is \(F(x)=x^3\sin(x)\).

Answer

\(F(x)=x^3\sin(x)\)
Antiderivatives and indefinite integrals 62
Differentiate \(F\) to determine whether it is an antiderivative of \(f\). a) \(f(x)=5(2x-4)(x^2-4x)^4\) and \(F(x)=(x^2-4x)^5+12\) b) \(f(x)=\frac{x}{\sqrt{x^2+1}}\) and \(F(x)=\sqrt{x^2+1}+4\)

Hints

- Use the chain rule: derivative of the outer function times derivative of the inner function. - Rewrite a square root as a power when helpful. - Identify the inner expression in each part. - Compare the complete derivative with \(f\).

Solution

1. For part a, use the chain rule: \(F'(x)=5(x^2-4x)^4(2x-4)\). This equals \(f(x)\), so \(F\) is an antiderivative of \(f\). 2. For part b, write \(F(x)=(x^2+1)^{\frac{1}{2}}+4\). Then \(F'(x)=\frac{1}{2}(x^2+1)^{-\frac{1}{2}}(2x)=\frac{x}{\sqrt{x^2+1}}=f(x)\). Thus, \(F\) is an antiderivative of \(f\).

Answer

a) Yes, \(F\) is an antiderivative of \(f\). b) Yes, \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 63
Let \(f(x)=(x+2)^2-3x^3\). Find and simplify \(f^{\prime}(x)\) and one antiderivative \(F(x)\).

Hints

- Expand the squared binomial first. - Apply the derivative and antiderivative power rules term by term. - Differentiate the antiderivative to check it.

Solution

1. Expand the function: \(f(x)=x^2+4x+4-3x^3\). 2. Differentiate term by term: \(f^{\prime}(x)=-9x^2+2x+4\). 3. Integrate term by term: \(F(x)=-\frac34x^4+\frac13x^3+2x^2+4x\).

Answer

\(f^{\prime}(x)=-9x^2+2x+4\) \(F(x)=-\frac34x^4+\frac13x^3+2x^2+4x\)
Antiderivatives and indefinite integrals 64
Let \(g(x)=3\cos x-4e^x\). a) Find \(g'(x)\) and \(g''(x)\). b) Find one antiderivative \(G\) of \(g\). c) Find the slope of the graph of \(g\) at \(x=0\).

Hints

- Differentiate and integrate each term separately. - Track the signs for sine and cosine. - Remember that \(e^x\) is its own derivative and antiderivative. - Use the first derivative to find slope at a point.

Solution

1. Differentiate term by term: \(g'(x)=-3\sin x-4e^x\). Differentiating again gives \(g''(x)=-3\cos x-4e^x\). 2. Integrate term by term. One antiderivative is \(G(x)=3\sin x-4e^x\). More generally, \(G(x)=3\sin x-4e^x+C\). 3. The slope at \(x=0\) is \(g'(0)=-3\sin 0-4e^0=-4\).

Answer

a) \(g'(x)=-3\sin x-4e^x\); \(g''(x)=-3\cos x-4e^x\) b) \(G(x)=3\sin x-4e^x\) c) The slope is \(-4\).
Antiderivatives and indefinite integrals 65
Let \(f(x)=4e^x-\frac{1}{2}x^4+\sin x\). Find \(f'(x)\), \(f''(x)\), and the general antiderivative \(F(x)\).

Hints

- Work term by term using the sum rule. - Use the basic derivative and antiderivative rules for powers, exponential functions, sine, and cosine. - Check the signs of the trigonometric terms. - Include an arbitrary constant in the general antiderivative.

Solution

1. Differentiate term by term: \(f'(x)=4e^x-2x^3+\cos x\). 2. Differentiate again: \(f''(x)=4e^x-6x^2-\sin x\). 3. Integrate the original function term by term: \(F(x)=4e^x-\frac{1}{10}x^5-\cos x+C\). Differentiating this expression returns \(f(x)\).

Answer

\(f'(x)=4e^x-2x^3+\cos x\) \(f''(x)=4e^x-6x^2-\sin x\) \(F(x)=4e^x-\frac{1}{10}x^5-\cos x+C\)
Antiderivatives and indefinite integrals 66
Let \(g(x)=2x^2-3e^x+1\). a) Find \(g'(x)\) and \(g''(x)\). b) Find the antiderivative \(G\) of \(g\) whose graph passes through \((0, 2)\).

Hints

- Differentiate and integrate each term separately. - Include an arbitrary constant in the general antiderivative. - Substitute the coordinates of the given point into \(G\). - Use \(e^0=1\) to solve for the constant.

Solution

1. Differentiate term by term: \(g'(x)=4x-3e^x\) and \(g''(x)=4-3e^x\). 2. The general antiderivative is \(G(x)=\frac{2}{3}x^3-3e^x+x+C\). Use the condition \(G(0)=2\): \(-3+C=2\), so \(C=5\). Therefore, \(G(x)=\frac{2}{3}x^3-3e^x+x+5\).

Answer

a) \(g'(x)=4x-3e^x\); \(g''(x)=4-3e^x\) b) \(G(x)=\frac{2}{3}x^3-3e^x+x+5\)
Antiderivatives and indefinite integrals 67
Determine algebraically whether \(F(x)=(x^2-3x)e^{2x}\) is an antiderivative of \(f(x)=(2x^2-4x-3)e^{2x}\).

Hints

- What derivative relationship defines an antiderivative? - Use the product rule. - Remember the chain-rule factor when differentiating \(e^{2x}\). - Factor out the common exponential term before comparing.

Solution

1. Use the product rule with \(u(x)=x^2-3x\) and \(v(x)=e^{2x}\). 2. Their derivatives are \(u'(x)=2x-3\) and \(v'(x)=2e^{2x}\). 3. Therefore, \(F'(x)=(2x-3)e^{2x}+2(x^2-3x)e^{2x}\). 4. Factor and simplify: \(F'(x)=e^{2x}(2x-3+2x^2-6x)=(2x^2-4x-3)e^{2x}=f(x)\). 5. Hence, \(F\) is an antiderivative of \(f\).

Answer

Yes. \(F^{\prime}(x)=(2x^2-4x-3)e^{2x}=f(x)\), so \(F\) is an antiderivative of \(f\).
Antiderivatives and indefinite integrals 68
Let \(f(x)=(x^2+4x+2)e^x\) for all real \(x\). a) Find the zeros of \(f\). b) Show that \(F(x)=(x^2+2x)e^x\) is an antiderivative of \(f\). Then find an antiderivative \(G\) of \(f\) that satisfies \(G(-2)=1\).

Hints

- Use the zero-product property in part a. - Recall the quadratic formula. - Differentiate \(F\) to verify the antiderivative relationship. - Antiderivatives differ by a constant; use the initial value to find it.

Solution

1. For part a, \(e^x>0\), so the zeros satisfy \(x^2+4x+2=0\). 2. The quadratic formula gives \(x=\frac{-4\pm\sqrt{16-8}}{2}=-2\pm\sqrt{2}\). 3. For part b, differentiate using the product rule: \(F'(x)=(2x+2)e^x+(x^2+2x)e^x=(x^2+4x+2)e^x=f(x)\). 4. Every antiderivative has the form \(G(x)=F(x)+C\). Since \(F(-2)=0\), the condition \(G(-2)=1\) gives \(C=1\). 5. Therefore, \(G(x)=(x^2+2x)e^x+1\).

Answer

a) \(x=-2-\sqrt{2}\) and \(x=-2+\sqrt{2}\) b) \(F'(x)=f(x)\), and \(G(x)=(x^2+2x)e^x+1\)
Antiderivatives and indefinite integrals 69
Let \(f(x)=(x^2+5x+5)e^x\). Differentiate each candidate to determine which one is an antiderivative of \(f\). 1. \(F_A(x)=(x^2+5x+5)e^x\) 2. \(F_B(x)=(x^2+4x+1)e^x\) 3. \(F_C(x)=(x^2+3x+2)e^x+4\) 4. \(F_D(x)=(x^2+7x+10)e^x\)

Hints

- Differentiate each candidate and compare it with \(f\). - Use the product rule for a polynomial times \(e^x\). - What happens to an added constant when differentiated? - Compare the polynomial coefficients after factoring out \(e^x\).

Solution

1. Differentiate each product using the product rule. 2. \(F_A'(x)=(x^2+7x+10)e^x\ne f(x)\). 3. \(F_B'(x)=(x^2+6x+5)e^x\ne f(x)\). 4. \(F_C'(x)=(x^2+5x+5)e^x=f(x)\). The constant \(4\) differentiates to \(0\). 5. \(F_D'(x)=(x^2+9x+17)e^x\ne f(x)\). 6. Therefore, \(F_C\) is an antiderivative of \(f\).

Answer

\(F_C(x)=(x^2+3x+2)e^x+4\)
Antiderivatives and indefinite integrals 70
The function \(F(x)=(ax^2+bx+c)e^x\) is an antiderivative of \(f(x)=(x^2-x-2)e^x\). Find \(a\), \(b\), and \(c\).

Hints

- Use \(F'(x)=f(x)\). - Differentiate with the product rule and factor out \(e^x\). - Equal polynomials have matching coefficients. - Solve the resulting three equations in order.

Solution

1. Differentiate \(F\) using the product rule: \(F'(x)=(2ax+b)e^x+(ax^2+bx+c)e^x\). 2. Combine terms: \(F'(x)=[ax^2+(2a+b)x+(b+c)]e^x\). 3. Match coefficients with \((x^2-x-2)e^x\): \(a=1\), \(2a+b=-1\), and \(b+c=-2\). 4. From \(a=1\), \(2+b=-1\), so \(b=-3\). Then \(-3+c=-2\), so \(c=1\). 5. Therefore, \(a=1\), \(b=-3\), and \(c=1\).

Answer

\(a=1\), \(b=-3\), \(c=1\)
Antiderivatives and indefinite integrals 71
Let \(f(x)=4e^{2x}-\frac{1}{2}x^2+\sin(x)\). Find the antiderivative \(F\) whose graph passes through \((0, 3)\).

Hints

- Which integration rules apply to the exponential, polynomial, and sine terms? - How does the coefficient in the exponent affect the antiderivative? - What equation does the point on the graph provide? - Use that equation to determine \(C\).

Solution

1. Integrate term by term: \(F(x)=2e^{2x}-\frac{1}{6}x^3-\cos(x)+C\). 2. Use \(F(0)=3\): \(2e^0-0-\cos(0)+C=3\). 3. This gives \(2-1+C=3\), so \(C=2\). 4. Therefore, \(F(x)=2e^{2x}-\frac{1}{6}x^3-\cos(x)+2\).

Answer

\(F(x)=2e^{2x}-\frac{1}{6}x^3-\cos(x)+2\)
Antiderivatives and indefinite integrals 72
Determine whether \(F(x)=x^{-1}(x^2-4)^2\) is an antiderivative of \(f(x)=\frac{3x^4-8x^2+16}{x^2}\).

Hints

- Differentiate \(F\) and compare the result with \(f\). - Expand and simplify \(F\) before differentiating. - Track signs carefully when differentiating negative powers. - Compare the numerators after using a common denominator.

Solution

1. Expand and simplify: \(F(x)=\frac{x^4-8x^2+16}{x}=x^3-8x+16x^{-1}\). 2. Differentiate: \(F'(x)=3x^2-8-16x^{-2}\). 3. With a common denominator, \(F'(x)=\frac{3x^4-8x^2-16}{x^2}\). 4. The constant term in the numerator is \(-16\), not \(+16\). Therefore, \(F'(x)\ne f(x)\), so \(F\) is not an antiderivative of \(f\).

Answer

No, \(F\) is not an antiderivative of \(f\).
Antiderivatives and indefinite integrals 73
For \(n\ge2\), let \(f_n(x)=\frac{3}{x^n}\) for \(x>0\). 1. Find the general form of the antiderivatives \(F_n\). 2. Explain how many different antiderivatives exist for a fixed value of \(n\). 3. For \(n=4\), find the antiderivative whose graph passes through \(P(1, 1)\).

Hints

- Rewrite the quotient using a negative exponent. - Apply the power rule for antiderivatives. - Different constants give different antiderivatives. - Substitute the given point to determine the constant.

Solution

1. Rewrite \(f_n(x)=3x^{-n}\). By the power rule, \(F_n(x)=\frac{3}{1-n}x^{1-n}+C=-\frac{3}{(n-1)x^{n-1}}+C\). 2. For each fixed \(n\), there are infinitely many antiderivatives because \(C\) can be any real number. 3. For \(n=4\), \(F_4(x)=-\frac1{x^3}+C\). Use \(F_4(1)=1\): \(-1+C=1\), so \(C=2\). Therefore, \(F_4(x)=-\frac1{x^3}+2\).

Answer

1. \(F_n(x)=-\frac{3}{(n-1)x^{n-1}}+C\), where \(C\in\mathbb R\) 2. Infinitely many 3. \(F_4(x)=-\frac1{x^3}+2\)
Antiderivatives and indefinite integrals 74
Match each function \(f_A\) through \(f_D\) with the correct antiderivative \(F_1\) through \(F_4\) by differentiating. (A) \(f_A(x)=\frac{10}{(x+5)^2}\) (B) \(f_B(x)=\frac{x^2-2x}{(x-1)^2}\) (C) \(f_C(x)=-12x^{-4}\) (D) \(f_D(x)=\frac{4}{x^5}\) (1) \(F_1(x)=\frac{x^2}{x-1}\) (2) \(F_2(x)=-\frac{1}{x^4}\) (3) \(F_3(x)=\frac{2x}{x+5}\) (4) \(F_4(x)=\frac{4}{x^3}\)

Hints

- The derivative of an antiderivative must equal the original function. - Use the quotient rule for rational functions with variable expressions in both numerator and denominator. - Rewrite reciprocal powers using negative exponents. - Simplify each derivative carefully before matching.

Solution

1. Differentiate \(F_1\): \(F_1'(x)=\frac{2x(x-1)-x^2}{(x-1)^2}=\frac{x^2-2x}{(x-1)^2}=f_B(x)\). 2. Differentiate \(F_2(x)=-x^{-4}\): \(F_2'(x)=4x^{-5}=\frac{4}{x^5}=f_D(x)\). 3. Differentiate \(F_3\) using the quotient rule: \(F_3'(x)=\frac{2(x+5)-2x}{(x+5)^2}=\frac{10}{(x+5)^2}=f_A(x)\). 4. Differentiate \(F_4(x)=4x^{-3}\): \(F_4'(x)=-12x^{-4}=f_C(x)\).

Answer

(A)–(3); (B)–(1); (C)–(4); (D)–(2)
Antiderivatives and indefinite integrals 75
Let \(f(x)=\frac{2}{3x}-4\) for \(x<0\). 1. Give the family of all antiderivatives of \(f\) on \(x<0\). 2. Find the antiderivative \(F_1\) whose graph passes through \((-1, 0)\). 3. Find another antiderivative \(F_2\) that satisfies \(F_2(-e)=1\).

Hints

- Recall the antiderivative of \(x^{-1}\). - Account for the sign of the logarithm's argument when \(x<0\). - Substitute each given function value into the general antiderivative to find \(C\). - Use basic logarithm values when simplifying.

Solution

1. On \(x<0\), the family of antiderivatives is \(F(x)=\frac{2}{3}\ln(-x)-4x+C\). 2. Use \(F_1(-1)=0\): \(\frac{2}{3}\ln(1)+4+C=0\). Since \(\ln(1)=0\), \(C=-4\). Thus, \(F_1(x)=\frac{2}{3}\ln(-x)-4x-4\). 3. Use \(F_2(-e)=1\): \(\frac{2}{3}\ln(e)+4e+C=1\). Therefore, \(\frac{2}{3}+4e+C=1\), so \(C=\frac{1}{3}-4e\). 4. Hence, \(F_2(x)=\frac{2}{3}\ln(-x)-4x+\frac{1}{3}-4e\).

Answer

1. \(F(x)=\frac{2}{3}\ln(-x)-4x+C\) 2. \(F_1(x)=\frac{2}{3}\ln(-x)-4x-4\) 3. \(F_2(x)=\frac{2}{3}\ln(-x)-4x+\frac{1}{3}-4e\)
Antiderivatives and indefinite integrals 76
Let \(g(x)=\frac{5}{x}+\frac{1}{2}x\) with domain \(\mathbb{R}\setminus\{0\}\). 1. Show by differentiating that \(G(x)=5\ln(-x)+\frac{1}{4}x^2+7\) is an antiderivative of \(g\) for \(x<0\). 2. Find an antiderivative \(H\) of \(g\) for \(x>0\) that satisfies \(H(1)=0.25\).

Hints

- Differentiate \(G\) and compare it with \(g\). - Use the chain rule for \(\ln(-x)\). - For \(x>0\), integrate the reciprocal and polynomial terms. - Use the given function value to determine \(C\).

Solution

1. For \(x<0\), \(G'(x)=5\left(\frac{1}{-x}\right)(-1)+\frac{1}{2}x=\frac{5}{x}+\frac{1}{2}x=g(x)\). 2. For \(x>0\), the general antiderivative is \(H(x)=5\ln(x)+\frac{1}{4}x^2+C\). 3. Apply \(H(1)=0.25\): \(5\ln(1)+\frac{1}{4}+C=0.25\). 4. Since \(\ln(1)=0\) and \(\frac{1}{4}=0.25\), \(C=0\). Therefore, \(H(x)=5\ln(x)+\frac{1}{4}x^2\).

Answer

1. \(G'(x)=g(x)\) for \(x<0\). 2. \(H(x)=5\ln(x)+\frac{1}{4}x^2\)
Antiderivatives and indefinite integrals 77
Let \(f(x)=\frac{1}{x+4}\) for \(x\in\mathbb{R}\setminus\{-4\}\). Decide whether \(F(x)=\begin{cases}\ln(x+4)-2&\text{for }x>-4\\\ln(-x-4)+5&\text{for }x<-4\end{cases}\) is an antiderivative of \(f\). Justify your answer.

Hints

- Check the derivative separately on each interval of the domain. - Use the chain rule for the logarithm in the region \(x<-4\). - Does a disconnected domain require the same additive constant on both components? - Compare the derivative with \(f\) on each interval.

Solution

1. For \(x>-4\), \(F'(x)=\frac{d}{dx}[\ln(x+4)-2]=\frac{1}{x+4}\). 2. For \(x<-4\), \(F'(x)=\frac{d}{dx}[\ln(-x-4)+5]=\frac{1}{-x-4}(-1)=\frac{1}{x+4}\). 3. Thus, \(F'(x)=f(x)\) on both components of the domain. 4. The different additive constants are allowed because the domain consists of two disconnected intervals. Therefore, \(F\) is an antiderivative of \(f\).

Answer

Yes. \(F^{\prime}(x)=f(x)\) on both \((-\infty, -4)\) and \((-4, \infty)\).
Antiderivatives and indefinite integrals 78
Let \(f(x)=(2x+1)e^{2x}\). Differentiate to determine which function \(F_1\) through \(F_4\) is an antiderivative of \(f\). (1) \(F_1(x)=xe^{2x}+7\) (2) \(F_2(x)=(x+1)e^{2x}\) (3) \(F_3(x)=e^{2x}\) (4) \(F_4(x)=2xe^x\)

Hints

- Use the product rule. - Include the chain-rule factor when differentiating \(e^{2x}\). - Differentiate the candidates and compare each result with \(f\).

Solution

1. Differentiate \(F_1(x)=xe^{2x}+7\) using the product and chain rules. 2. \(F_1'(x)=e^{2x}+2xe^{2x}=(2x+1)e^{2x}=f(x)\). 3. The other derivatives are \(F_2'(x)=(2x+3)e^{2x}\), \(F_3'(x)=2e^{2x}\), and \(F_4'(x)=(2x+2)e^x\). 4. Therefore, only \(F_1\) is an antiderivative of \(f\).

Answer

\(F_1(x)=xe^{2x}+7\)
Antiderivatives and indefinite integrals 79
Let \(g(x)=2-\ln(5-x)\). a) State the maximal domain of \(g\). b) Verify that \(G(x)=3x+(5-x)\ln(5-x)\) is an antiderivative of \(g\) on that domain. c) Find the antiderivative \(H\) of \(g\) whose graph passes through \((4, 0)\). d) Explain why every antiderivative of \(g\) on its domain has the form \(G(x)+C\).

Hints

- Require the logarithm's input to be positive. - Use both the product rule and the chain rule when differentiating \((5-x)\ln(5-x)\). - Add a constant to the verified antiderivative and use the given point. - Recall the constant-difference property on a connected interval.

Solution

1. The logarithm requires \(5-x>0\), so the maximal domain is \((-\infty, 5)\). 2. Differentiate using the product and chain rules: \(G'(x)=3-\ln(5-x)-1=2-\ln(5-x)=g(x)\). Thus, \(G\) is an antiderivative of \(g\). 3. Write \(H(x)=G(x)+C\). Since \(H(4)=0\), \(0=3\cdot4+(5-4)\ln(1)+C=12+C\), so \(C=-12\). Therefore, \(H(x)=3x+(5-x)\ln(5-x)-12\). 4. The domain \((-\infty, 5)\) is one connected interval. On a connected interval, any two antiderivatives of the same function differ by a constant.

Answer

a) \((-\infty, 5)\) b) \(G'(x)=2-\ln(5-x)=g(x)\) c) \(H(x)=3x+(5-x)\ln(5-x)-12\) d) The domain is connected, so any two antiderivatives differ by one constant.
Antiderivatives and indefinite integrals 80
Let \(f(x)=\frac{\ln(x)}{x}\) for \(x>0\). 1. Show that \(F(x)=\frac{1}{2}[\ln(x)]^2\) is an antiderivative of \(f\). 2. Find an antiderivative \(G\) of \(f\) that satisfies \(G(e)=0\).

Hints

- Differentiate \(F\) to verify the antiderivative relationship. - Use the chain rule for a squared logarithm. - How do all antiderivatives of the same function differ? - Use the logarithm value at the given input when solving for \(C\).

Solution

1. Differentiate using the chain rule: \(F'(x)=\frac{1}{2}\cdot2\ln(x)\cdot\frac{1}{x}=\frac{\ln(x)}{x}=f(x)\). 2. Every antiderivative has the form \(G(x)=\frac{1}{2}[\ln(x)]^2+C\). 3. Use \(G(e)=0\): \(\frac{1}{2}[\ln(e)]^2+C=0\). 4. Since \(\ln(e)=1\), \(C=-\frac{1}{2}\). Thus, \(G(x)=\frac{1}{2}[\ln(x)]^2-\frac{1}{2}\).

Answer

1. \(F'(x)=\frac{\ln(x)}{x}=f(x)\). 2. \(G(x)=\frac{1}{2}[\ln(x)]^2-\frac{1}{2}\)
Antiderivatives and indefinite integrals 81
Let \(f(x)=x^2\ln(x)\) for \(x>0\). 1. Show that \(F(x)=\frac{1}{9}x^3(3\ln(x)-1)\) is an antiderivative of \(f\). 2. Another antiderivative \(H\) of \(f\) passes through \((1, 1)\). Find \(H(x)\).

Hints

- Differentiate the proposed antiderivative. - Use the product rule on the term containing \(x^3\ln(x)\). - All antiderivatives differ by a constant. - Substitute the point to determine that constant.

Solution

1. Rewrite \(F(x)=\frac{1}{3}x^3\ln(x)-\frac{1}{9}x^3\). 2. Differentiate using the product rule: \(F'(x)=x^2\ln(x)+\frac{1}{3}x^2-\frac{1}{3}x^2=x^2\ln(x)=f(x)\). 3. Every antiderivative has the form \(H(x)=\frac{1}{9}x^3(3\ln(x)-1)+C\). 4. Use \(H(1)=1\): \(-\frac{1}{9}+C=1\), so \(C=\frac{10}{9}\). 5. Therefore, \(H(x)=\frac{1}{9}x^3(3\ln(x)-1)+\frac{10}{9}\).

Answer

1. \(F'(x)=x^2\ln(x)=f(x)\). 2. \(H(x)=\frac{1}{9}x^3(3\ln(x)-1)+\frac{10}{9}\)
Antiderivatives and indefinite integrals 82
Let \(f(x)=x-\frac{1}{4x}\) for \(x<0\). Find two different antiderivatives of \(f\).

Hints

- Pay attention to the logarithm's argument because \(x<0\). - Use the chain rule to check the derivative of \(\ln(-x)\). - Different constants give different antiderivatives.

Solution

1. Integrate term by term. An antiderivative of \(x\) is \(\frac12x^2\). 2. On \(x<0\), an antiderivative of \(\frac1x\) is \(\ln(-x)\). Therefore, a general antiderivative is \(F(x)=\frac12x^2-\frac14\ln(-x)+C\). 3. Choosing \(C=0\) and \(C=-1\) gives two different antiderivatives.

Answer

\(F_1(x)=\frac12x^2-\frac14\ln(-x)\) and \(F_2(x)=\frac12x^2-\frac14\ln(-x)-1\)
Antiderivatives and indefinite integrals 83
Two functions \(F\) and \(G\) are antiderivatives of the same function \(f\) on \(\mathbb{R}\). a) Given \(F(x)=\frac{1}{2}x^4-x^2+3\), find \(f(x)\). b) Find \(G(x)\) if its graph passes through \((2, 10)\). c) Explain generally why the difference between any two antiderivatives of the same function on an interval is constant.

Hints

- Differentiate an antiderivative to recover the original function. - Use the stated point to distinguish one function from a family of possible functions. - In part c), what derivative do you get if you subtract the two functions first?

Solution

1. Since \(F\) is an antiderivative of \(f\), \(f(x)=F'(x)=2x^3-2x\). 2. Every antiderivative of \(f\) on \(\mathbb{R}\) has the form \(G(x)=\frac{1}{2}x^4-x^2+C\). 3. Use \(G(2)=10\): \(8-4+C=10\), so \(C=6\). Thus, \(G(x)=\frac{1}{2}x^4-x^2+6\). 4. If \(F\) and \(G\) are antiderivatives of the same function on a common interval, then \((G-F)'=G'-F'=f-f=0\). A function with derivative \(0\) throughout an interval is constant there.

Answer

a) \(f(x)=2x^3-2x\) b) \(G(x)=\frac{1}{2}x^4-x^2+6\) c) On any common interval, \((G-F)'=0\), so \(G-F\) is constant.
Antiderivatives and indefinite integrals 84
For \(x\ne0\), give two different antiderivatives of \(f(x)=\frac{6x^4-3}{x^2}+5x^4\).

Hints

- Divide each term in the numerator by \(x^2\) before integrating. - Rewrite reciprocal powers using negative exponents. - Adding a constant to an antiderivative produces another antiderivative.

Solution

1. Simplify the function: \(f(x)=6x^2-3x^{-2}+5x^4\). 2. Integrating term by term gives an antiderivative \(F(x)=2x^3+3x^{-1}+x^5=x^5+2x^3+\frac3x\). 3. Adding different constants, such as \(0\) and \(5\), gives two different antiderivatives.

Answer

\(F_1(x)=x^5+2x^3+\frac3x\) \(F_2(x)=x^5+2x^3+\frac3x+5\)
Antiderivatives and indefinite integrals 85
For \(x>0\), find two different antiderivatives of \(g(x)=(2x^2+1)^2-\frac4{\sqrt{x}}\).

Hints

- Expand the squared binomial first. - Rewrite the radical in the denominator using a negative exponent. - Integrate the resulting sum term by term. - Different constants produce different antiderivatives.

Solution

1. Expand and rewrite the function: \(g(x)=4x^4+4x^2+1-4x^{-1/2}\). 2. Integrating term by term gives \(G(x)=\frac45x^5+\frac43x^3+x-8\sqrt{x}+C\). 3. Choosing \(C=0\) and \(C=1\) gives two different antiderivatives.

Answer

\(G_1(x)=\frac45x^5+\frac43x^3+x-8\sqrt{x}\) \(G_2(x)=\frac45x^5+\frac43x^3+x-8\sqrt{x}+1\)
Antiderivatives and indefinite integrals 86
Let \(h(x)=\frac{1}{k+1}x^k-kx^{k-1}\), where \(k\in\mathbb{N}\) and \(k\ge1\). Find one antiderivative \(H\) of \(h\).

Hints

- Treat the parameter \(k\) as a constant. - Apply the reverse power rule to each term. - Differentiate your result to verify it.

Solution

1. Treat \(k\) as a constant and integrate each term with respect to \(x\). 2. The first term gives \(\frac{1}{k+1}\cdot\frac{x^{k+1}}{k+1}=\frac{x^{k+1}}{(k+1)^2}\). 3. The second term gives \(-k\cdot\frac{x^k}{k}=-x^k\). 4. Therefore, \(H(x)=\frac{x^{k+1}}{(k+1)^2}-x^k\).

Answer

\(H(x)=\frac{x^{k+1}}{(k+1)^2}-x^k\)
Antiderivatives and indefinite integrals 87
Find one antiderivative \(F\) of each function. a) \(f(x)=(3x-1)^2\) b) \(f(x)=\frac12x^2(x+4)\) c) \(f(x)=\frac{x^4-2x^2+6}{x^2}\), for \(x\ne0\) d) \(f(x)=p(x-p)^2\), where \(p\in\mathbb{R}\)

Hints

- Rewrite each function as a sum of powers before integrating. - Expand products and squared binomials when needed. - Rewrite terms with \(x\) in the denominator using negative exponents. - Treat \(p\) as a constant when integrating with respect to \(x\).

Solution

1. For a), expand to \(9x^2-6x+1\), then integrate term by term: \(F(x)=3x^3-3x^2+x\). 2. For b), expand to \(\frac12x^3+2x^2\), then integrate: \(F(x)=\frac18x^4+\frac23x^3\). 3. For c), simplify to \(x^2-2+6x^{-2}\), then integrate: \(F(x)=\frac13x^3-2x-\frac6x\). 4. For d), treat \(p\) as a constant. Expanding gives \(px^2-2p^2x+p^3\), so \(F(x)=\frac p3x^3-p^2x^2+p^3x\).

Answer

a) \(F(x)=3x^3-3x^2+x\) b) \(F(x)=\frac18x^4+\frac23x^3\) c) \(F(x)=\frac13x^3-2x-\frac6x\) d) \(F(x)=\frac p3x^3-p^2x^2+p^3x\)
Antiderivatives and indefinite integrals 88
Find one antiderivative \(F\) of each function. a) \(f(x)=(1-x)^3\) b) \(f(x)=\frac{4\sqrt{x^7}-2}{\sqrt{x}}\), for \(x>0\) c) \(f(x)=(x^2+2)^2\) d) \(f(x)=\frac{x^5-3x^2+2}{x^4}\), for \(x\ne0\)

Hints

- Expand powers of binomials before integrating. - Use exponent rules to simplify quotients. - Rewrite radicals and reciprocal powers using rational or negative exponents. - Differentiate each result to check it.

Solution

1. For a), expand to \(1-3x+3x^2-x^3\). Integrating term by term gives \(F(x)=x-\frac32x^2+x^3-\frac14x^4\). 2. For b), simplify to \(4x^3-2x^{-1/2}\). Integrating gives \(F(x)=x^4-4\sqrt{x}\). 3. For c), expand to \(x^4+4x^2+4\). Integrating gives \(F(x)=\frac15x^5+\frac43x^3+4x\). 4. For d), simplify to \(x-3x^{-2}+2x^{-4}\). Integrating gives \(F(x)=\frac12x^2+\frac3x-\frac{2}{3x^3}\).

Answer

a) \(F(x)=x-\frac32x^2+x^3-\frac14x^4\) b) \(F(x)=x^4-4\sqrt{x}\) c) \(F(x)=\frac15x^5+\frac43x^3+4x\) d) \(F(x)=\frac12x^2+\frac3x-\frac{2}{3x^3}\)
Antiderivatives and indefinite integrals 89
Let \(f(x)=4e^{2x}-6x^2\). Find the antiderivative \(F\) that satisfies \(F(0)=5\).

Hints

- Account for the chain-rule factor when integrating \(e^{2x}\). - Evaluate the exponential term at the given input. - Use the given function value to find \(C\). - Differentiate your result to check it.

Solution

1. Integrate term by term: \(F(x)=2e^{2x}-2x^3+C\). 2. Apply \(F(0)=5\): \(2e^0+C=5\). 3. Thus, \(2+C=5\), so \(C=3\). 4. Therefore, \(F(x)=2e^{2x}-2x^3+3\).

Answer

\(F(x)=2e^{2x}-2x^3+3\)
Antiderivatives and indefinite integrals 90
The functions \(F\) and \(G\) are antiderivatives of the same function \(f\). Let \(F(x)=\frac{1}{x}+x^2\) for \(x>0\), and suppose the graph of \(G\) passes through \((1, 5)\). Find \(G(x)\) and \(f(x)\).

Hints

- How do antiderivatives of the same function differ? - Use the point on \(G\) to determine the constant. - Differentiate \(F\) to recover \(f\).

Solution

1. Since \(F\) and \(G\) are antiderivatives of the same function, \(G(x)=F(x)+C=\frac{1}{x}+x^2+C\). 2. Use \(G(1)=5\): \(1+1+C=5\), so \(C=3\). Thus, \(G(x)=\frac{1}{x}+x^2+3\). 3. Differentiate \(F\) to recover \(f\): \(f(x)=F'(x)=-\frac{1}{x^2}+2x\).

Answer

\(G(x)=\frac{1}{x}+x^2+3\) \(f(x)=-\frac{1}{x^2}+2x\)
Antiderivatives and indefinite integrals 91
Let \(f(x)=\frac{1}{x}\) on the domain \(x<0\). a) Give three different antiderivatives of \(f\). b) Explain without further calculation why all antiderivatives of \(f\) have the same slope at \(x=-2\). State that slope.

Hints

- Which logarithmic function differentiates to \(\frac{1}{x}\) when \(x<0\)? - Different antiderivatives differ only by constants. - How is the slope of an antiderivative related to \(f\)? - Evaluate \(f\) at the stated input.

Solution

1. On \(x<0\), the family of antiderivatives is \(F(x)=\ln(-x)+C\). 2. Three examples are \(F_1(x)=\ln(-x)\), \(F_2(x)=\ln(-x)+2\), and \(F_3(x)=\ln(-x)-1\). 3. Every antiderivative satisfies \(F'(x)=f(x)\), so the slope at \(x=-2\) is always \(f(-2)\). 4. Since \(f(-2)=-\frac{1}{2}\), all the antiderivatives have slope \(-\frac{1}{2}\) there.

Answer

a) \(F_1(x)=\ln(-x)\), \(F_2(x)=\ln(-x)+2\), and \(F_3(x)=\ln(-x)-1\) b) All have slope \(f(-2)=-\frac{1}{2}\).
Antiderivatives and indefinite integrals 92
The graph of the derivative \(f'\) of a function \(f\) is shown. The graph of \(f\) passes through \((2, 1)\). Find an equation for \(f\).
Figure for problem 532414

Hints

- Read the slope and y-intercept of the line from the graph. - Integrate the derivative and include a constant \(C\). - Use the given point to determine \(C\).

Solution

1. The graph of \(f'\) is a line with y-intercept \(2\) and zero at \(x=4\). Its slope is \(\frac{0-2}{4-0}=-\frac{1}{2}\), so \(f'(x)=-\frac{1}{2}x+2\). 2. Integrate to obtain \(f(x)=-\frac{1}{4}x^2+2x+C\). 3. Use \(f(2)=1\): \(-1+4+C=1\), so \(C=-2\). 4. Therefore, \(f(x)=-\frac{1}{4}x^2+2x-2\).

Answer

\(f(x)=-\frac{1}{4}x^2+2x-2\)
Antiderivatives and indefinite integrals 93
The figures show three graphs: a function \(f\), its derivative \(f'\), and an antiderivative \(F\) of \(f\). Match graphs A, B, and C with \(f\), \(f'\), and \(F\). Justify your choices.
Figure for problem 532644

Hints

- Match local extrema of a graph with zeros of its derivative. - Compare increasing and decreasing intervals with the sign of the derivative. - Use the polynomial degrees to check the order \(F\), \(f\), and \(f'\).

Solution

1. Graph B has a local maximum at \(x = 2\) and a local minimum at \(x = 6\). Graph C is zero at those values, is negative on \((2, 6)\), and is positive outside that interval. Therefore, graph C is the derivative of graph B. 2. Graph C has a local minimum at \(x = 4\). Graph A is zero at \(x = 4\), is negative for \(x < 4\), and is positive for \(x > 4\). Therefore, graph A is the derivative of graph C. 3. Since \(F' = f\) and \(f'\) is the derivative of \(f\), graph B represents \(F\), graph C represents \(f\), and graph A represents \(f'\).

Answer

A \(\rightarrow f'\); B \(\rightarrow F\); C \(\rightarrow f\)
Antiderivatives and indefinite integrals 94
Let \(f(x)=x\ln x\) for \(x>0\). a) Verify that \(F(x)=\frac{1}{2}x^2\ln x-\frac{1}{4}x^2\) is an antiderivative of \(f\). b) Find the antiderivative \(H\) of \(f\) that satisfies \(H(1)=0\). c) Determine where \(H\) is decreasing and increasing from the sign of \(f\). Classify the point on the graph of \(H\) at \(x=1\).

Hints

- Differentiate the product \(x^2\ln x\) carefully and combine like terms. - Two antiderivatives of the same function differ by a constant; use \(H(1)=0\) to find it. - Determine the sign of \(x\ln x\) on \((0,1)\) and \((1,\infty)\). - A derivative changing from negative to positive identifies a minimum.

Solution

1. Differentiate using the product rule: \(F'(x)=x\ln x+\frac{1}{2}x-\frac{1}{2}x=x\ln x=f(x)\). Therefore, \(F\) is an antiderivative of \(f\). 2. Every antiderivative has the form \(H(x)=F(x)+C\). Since \(F(1)=-\frac{1}{4}\), the condition \(H(1)=0\) gives \(C=\frac{1}{4}\). Thus \(H(x)=\frac{1}{2}x^2\ln x-\frac{1}{4}x^2+\frac{1}{4}\). 3. Because \(H'(x)=f(x)=x\ln x\), and \(x>0\), the sign is determined by \(\ln x\): negative on \((0,1)\) and positive on \((1,\infty)\). Therefore \(H\) decreases on \((0,1)\) and increases on \((1,\infty)\). 4. Since \(H'\) changes from negative to positive at \(x=1\), \(H\) has an absolute minimum there. With \(H(1)=0\), the minimum point is \((1,0)\).

Answer

a) \(F'(x)=x\ln x=f(x)\), so \(F\) is an antiderivative of \(f\). b) \(H(x)=\frac{1}{2}x^2\ln x-\frac{1}{4}x^2+\frac{1}{4}\). c) \(H\) decreases on \((0,1)\), increases on \((1,\infty)\), and has an absolute minimum at \((1,0)\).
Antiderivatives and indefinite integrals 95
The graph of the derivative \(f^{\prime}\) is shown. The graph of \(f\) passes through \(P(3, 2)\). Find an equation for \(f\).
Figure for problem 533913

Hints

- Use the intercepts and vertex of the parabola to determine \(f^{\prime}\). - Integrate \(f^{\prime}\) and include a constant of integration. - Use the point on \(f\) to determine the constant.

Solution

1. The derivative has zeros at \(x=-2\) and \(x=2\) and a y-intercept of \(4\). Therefore, \(f^{\prime}(x)=-(x-2)(x+2)=4-x^2\). 2. Integrating gives \(f(x)=4x-\frac13x^3+C\). 3. Use \(f(3)=2\): \(2=12-9+C\), so \(C=-1\). 4. Thus, \(f(x)=-\frac13x^3+4x-1\).

Answer

\(f(x)=-\frac13x^3+4x-1\)
Antiderivatives and indefinite integrals 96
The graph of \(f\) is shown. Find an equation for the antiderivative \(F\) that satisfies \(F(2)=0\), and describe its graph.
Figure for problem 534431

Hints

- An antiderivative of a linear function is quadratic. - Use the zero of \(f\) to locate a horizontal tangent of \(F\). - Use \(F(2)=0\) to determine the vertical position of the graph.

Solution

1. The graph is the line \(f(x)=\frac12x-1\). 2. An antiderivative is \(F(x)=\frac14x^2-x+C\). 3. Use \(F(2)=0\): \(1-2+C=0\), so \(C=1\). 4. Therefore, \(F(x)=\frac14x^2-x+1=\frac14(x-2)^2\). Its graph is an upward-opening parabola with vertex \((2, 0)\).

Answer

\(F(x)=\frac14(x-2)^2\), an upward-opening parabola with vertex \((2, 0)\)
Antiderivatives and indefinite integrals 97
Let \(f(x)=\frac{2}{x+1}\) for \(x>-1\). Find the antiderivative \(F\) that satisfies \(F(0)=0\), and describe the monotonicity, concavity, and end behavior of its graph.

Hints

- Integrate the reciprocal linear expression and then use the initial condition. - The sign of \(F'=f\) determines whether \(F\) increases or decreases. - The behavior of \(f\) determines the concavity of \(F\). - Check the limits of the logarithm at both ends of its domain.

Solution

1. Integrating gives \(F(x)=2\ln(x+1)+C\). The condition \(F(0)=0\) gives \(C=0\), so \(F(x)=2\ln(x+1)\). 2. Since \(F'(x)=f(x)>0\) for \(x>-1\), \(F\) is strictly increasing. 3. Since \(f\) is decreasing, \(F''(x)=f'(x)<0\), so \(F\) is concave down. 4. As \(x\to-1^+\), \(F(x)\to-\infty\). As \(x\to\infty\), \(F(x)\to\infty\), even though the slope \(f(x)\to0\).

Answer

\(F(x)=2\ln(x+1)\). It is strictly increasing and concave down on \((-1,\infty)\). As \(x\to-1^+\), \(F(x)\to-\infty\); as \(x\to\infty\), \(F(x)\to\infty\) while its slope approaches \(0\).
Antiderivatives and indefinite integrals 98
Let \(f(x)=\sqrt{x}\) for \(x\ge0\). Find the antiderivative \(F\) that satisfies \(F(0)=-1\), and describe the shape of its graph.

Hints

- Rewrite the radical as a power before integrating. - Use \(F(0)=-1\) to determine the constant. - Use the sign and monotonicity of \(f=F'\) to describe \(F\).

Solution

1. Integrating gives \(F(x)=\frac23x^{3/2}+C\). 2. The condition \(F(0)=-1\) gives \(C=-1\), so \(F(x)=\frac23x^{3/2}-1\). 3. Since \(F'(x)=f(x)>0\) for \(x>0\), \(F\) is strictly increasing there. Since \(f\) is increasing, the slope of \(F\) increases, so \(F\) is concave up. 4. Because \(F'(0)=f(0)=0\), the graph begins at \((0,-1)\) with a horizontal tangent.

Answer

\(F(x)=\frac23x^{3/2}-1\). Its graph starts at \((0,-1)\) with a horizontal tangent and is increasing and concave up for \(x>0\).
Antiderivatives and indefinite integrals 99
A function \(F\) is an antiderivative of a function \(f\). The four panels show possible graphs of \(F\). You are told that \(F(0)=-2\), \(F(-2)=F(2)=0\), and \(F(x)\to1\) as \(x\to\pm\infty\). a) Identify the correct graph of \(F\). Justify your choice using the given values and end behavior. b) Using the graph you selected, determine where \(f\) is negative, zero, and positive. Justify your answer from where \(F\) is decreasing, has a horizontal tangent, or is increasing.
Figure for problem 534523

Hints

- Match all three kinds of information: the y-value at \(0\), the two zeros, and the horizontal end behavior. - Since \(F\) is an antiderivative of \(f\), the sign of \(f\) is determined by the slope of \(F\). - Read decreasing, horizontal-tangent, and increasing behavior directly from the chosen graph.

Solution

1. The correct graph must pass through \((0,-2)\), cross the x-axis at \(x=-2\) and \(x=2\), and approach the horizontal level \(y=1\) in both directions. Only Graph 1 has all of these features. 2. Because \(F'=f\), the sign of \(f\) is the sign of the slope of \(F\). 3. Graph 1 is decreasing for \(x<0\), has a horizontal tangent at \(x=0\), and is increasing for \(x>0\). 4. Therefore \(f(x)<0\) for \(x<0\), \(f(0)=0\), and \(f(x)>0\) for \(x>0\).

Answer

a) Graph 1 b) \(f(x)<0\) for \(x<0\), \(f(0)=0\), and \(f(x)>0\) for \(x>0\).
Antiderivatives and indefinite integrals 100
For \(k\ne 0\), let \(f_k(x)=\cos(kx)\). Find every antiderivative of \(f_k\) whose minimum value is exactly \(0\).

Hints

- Find the general antiderivative of \(\cos(kx)\). - Determine the range of \(\frac{1}{k}\sin(kx)\). - How does adding \(C\) shift the range vertically? - Set the minimum of the shifted range equal to \(0\).

Solution

1. The general antiderivative is \(F_k(x)=\frac{1}{k}\sin(kx)+C\). 2. Since \(\sin(kx)\) ranges from \(-1\) to \(1\), the term \(\frac{1}{k}\sin(kx)\) ranges from \(-\frac{1}{|k|}\) to \(\frac{1}{|k|}\). 3. Therefore, the minimum value of \(F_k\) is \(C-\frac{1}{|k|}\). 4. Set the minimum equal to \(0\): \(C-\frac{1}{|k|}=0\), so \(C=\frac{1}{|k|}\). 5. Thus \(F_k(x)=\frac{1}{k}\sin(kx)+\frac{1}{|k|}\).

Answer

\(F_k(x)=\frac{1}{k}\sin(kx)+\frac{1}{|k|}\)
Antiderivatives and indefinite integrals 101
Find the antiderivative \(F\) of \(f(x)=x^3-4x\) whose local minimum value is \(5\).

Hints

- How are \(f\) and an antiderivative \(F\) related? - Where can \(F\) have local extrema? - How can the derivative of \(f\) distinguish minima from maxima of \(F\)? - How does the stated minimum value determine \(C\)?

Solution

1. The general antiderivative is \(F(x)=\frac{1}{4}x^4-2x^2+C\). 2. Critical points of \(F\) occur where \(F'(x)=f(x)=0\): \(x(x^2-4)=0\), so \(x=-2, 0, 2\). 3. Since \(F''(x)=f'(x)=3x^2-4\), the points at \(x=\pm2\) are local minima and the point at \(x=0\) is a local maximum. 4. Use the required minimum value: \(F(2)=5\). Then \(\frac{1}{4}(2)^4-2(2)^2+C=5\), so \(4-8+C=5\) and \(C=9\). 5. Therefore, \(F(x)=\frac{1}{4}x^4-2x^2+9\).

Answer

\(F(x)=\frac{1}{4}x^4-2x^2+9\)
Antiderivatives and indefinite integrals 102
Let \(f(x)=\frac{1}{2}x-\frac{2}{x}\) for \(x>0\). Find the antiderivative \(F\) of \(f\) whose local minimum value is \(5-\ln(4)\).

Hints

- Which function has derivative \(\frac{1}{x}\)? - Set \(F'(x)=f(x)\) equal to zero to find critical points of \(F\). - Use logarithm properties when simplifying the condition. - The constant \(C\) shifts the graph vertically.

Solution

1. For \(x>0\), the general antiderivative is \(F(x)=\frac{1}{4}x^2-2\ln(x)+C\). 2. Critical points of \(F\) satisfy \(F'(x)=f(x)=0\): \(\frac{1}{2}x-\frac{2}{x}=0\), so \(x^2=4\). Because \(x>0\), \(x=2\). 3. Since \(F''(x)=f'(x)=\frac{1}{2}+\frac{2}{x^2}>0\), \(F\) has a local minimum at \(x=2\). 4. Apply the minimum value: \(F(2)=5-\ln(4)\). This gives \(1-2\ln(2)+C=5-\ln(4)\). 5. Because \(2\ln(2)=\ln(4)\), \(C=4\). Thus, \(F(x)=\frac{1}{4}x^2-2\ln(x)+4\).

Answer

\(F(x)=\frac{1}{4}x^2-2\ln(x)+4\)
Antiderivatives and indefinite integrals 103
Let \(f(x)=\frac{\cos(x)}{2\sqrt{x}}-\sqrt{x}\sin(x)\) for \(x>0\). Give one antiderivative \(F\) of \(f\).

Hints

- Which parts of the two terms are derivatives of each other? - Recall the relationship between \(\sqrt{x}\) and \(\frac{1}{2\sqrt{x}}\). - How does the negative sign relate to the derivative of cosine? - Try differentiating a product involving \(\sqrt{x}\) and \(\cos(x)\).

Solution

1. Look for a product whose derivative has the two given terms. 2. Let \(u(x)=\sqrt{x}\) and \(v(x)=\cos(x)\). Then \(u'(x)=\frac{1}{2\sqrt{x}}\) and \(v'(x)=-\sin(x)\). 3. By the product rule, \(\frac{d}{dx}[\sqrt{x}\cos(x)]=\frac{\cos(x)}{2\sqrt{x}}-\sqrt{x}\sin(x)=f(x)\). 4. Thus, one antiderivative is \(F(x)=\sqrt{x}\cos(x)\).

Answer

\(F(x)=\sqrt{x}\cos(x)\)
Antiderivatives and indefinite integrals 104
Let \(f(x)=\frac{x^2-4}{2x^2}\), where \(x\ne0\), and let \(F(x)=\frac{1}{2}x+4+\frac{2}{x}\). a) Show that \(F\) is an antiderivative of \(f\) on each interval \((-\infty, 0)\) and \((0, \infty)\). b) Find the antiderivative \(G\) of \(f\) on \((0, \infty)\) that satisfies \(G(2)=0\). c) Find the antiderivative \(H\) of \(f\) on \((-\infty, 0)\) that satisfies \(H(-2)=0\). d) Explain why the constants in \(G\) and \(H\) do not have to be the same.

Hints

- Simplify \(f\) or differentiate the reciprocal term directly. - On each connected interval, antiderivatives differ by a constant. - Use the given point on the positive interval to determine one constant and the point on the negative interval to determine the other. - Consider the role of the excluded input \(x=0\).

Solution

1. Differentiate \(F\): \(F'(x)=\frac{1}{2}-\frac{2}{x^2}=\frac{x^2-4}{2x^2}=f(x)\). Thus, \(F\) is an antiderivative of \(f\) wherever \(x\ne0\). 2. On \((0, \infty)\), write \(G(x)=F(x)+C\). Since \(F(2)=1+4+1=6\), the condition \(G(2)=0\) gives \(C=-6\). Therefore, \(G(x)=\frac{1}{2}x-2+\frac{2}{x}\). 3. On \((-\infty, 0)\), write \(H(x)=F(x)+D\). Since \(F(-2)=-1+4-1=2\), the condition \(H(-2)=0\) gives \(D=-2\). Therefore, \(H(x)=\frac{1}{2}x+2+\frac{2}{x}\). 4. The domain is split into two disconnected intervals by \(x=0\). A value condition on one interval does not determine the vertical shift on the other interval, so the two constants may differ.

Answer

a) \(F'(x)=f(x)\) for \(x\ne0\). b) \(G(x)=\frac{1}{2}x-2+\frac{2}{x}\) for \(x>0\) c) \(H(x)=\frac{1}{2}x+2+\frac{2}{x}\) for \(x<0\) d) The two domain intervals are disconnected, so each interval can have its own constant of integration.
Antiderivatives and indefinite integrals 105
Let \(h(x)=2+\frac{1}{x^2}\) and \(g(x)=2x-\frac{1}{x}\), where \(x\ne0\). a) Show that \(g\) is an antiderivative of \(h\). b) Maëlle says, “Every antiderivative of \(h\) on the domain \(x\ne0\) must equal \(g(x)+C\) for one real constant \(C\).” Explain why this statement is incomplete. c) Construct an antiderivative \(A\) of \(h\) on \(x\ne0\) that satisfies both \(A(1)=0\) and \(A(-1)=0\). Verify your result.

Hints

- Rewrite the reciprocal term as a negative power before differentiating. - Identify the connected intervals that make up the domain. - Determine one constant from \(A(1)=0\) and a separate constant from \(A(-1)=0\). - Verify the derivative on each branch of the piecewise function.

Solution

1. Differentiate \(g\): \(g'(x)=2+\frac{1}{x^2}=h(x)\), so \(g\) is an antiderivative on both intervals of the domain. 2. The domain \(x\ne0\) consists of the disconnected intervals \(( -\infty,0)\) and \((0,\infty)\). Antiderivatives may use one additive constant on the negative interval and a different additive constant on the positive interval. 3. Since \(g(1)=1\), the positive-domain formula needs constant \(-1\). Since \(g(-1)=-1\), the negative-domain formula needs constant \(1\). Thus, define \(A(x)=2x-\frac{1}{x}+1\) for \(x<0\), and \(A(x)=2x-\frac{1}{x}-1\) for \(x>0\). 4. Then \(A(-1)=0\) and \(A(1)=0\). Differentiating either branch gives \(2+\frac{1}{x^2}=h(x)\).

Answer

a) \(g'(x)=2+\frac{1}{x^2}=h(x)\). b) The domain has two disconnected intervals, so the additive constants may differ. c) \(A(x)=2x-\frac{1}{x}+1\) for \(x<0\), and \(A(x)=2x-\frac{1}{x}-1\) for \(x>0\).
Antiderivatives and indefinite integrals 106
Let \(g(x)=\begin{cases}2x+1&\text{for }x\ge0\\e^x&\text{for }x<0\end{cases}\) and \(G(x)=\begin{cases}x^2+x+2&\text{for }x\ge0\\e^x&\text{for }x<0\end{cases}\). Determine whether \(G\) is an antiderivative of \(g\) on all real numbers.

Hints

- What differentiability condition must an antiderivative satisfy? - Recall the relationship between differentiability and continuity. - Compare the one-sided behavior and the defined value of \(G\) at \(x=0\). - Is satisfying the derivative equation away from one point enough on all of \(\mathbb{R}\)?

Solution

1. Check continuity of \(G\) at \(x=0\). The defined value is \(G(0)=2\), while \(\lim_{x\to0^-}G(x)=e^0=1\). 2. Since the left-hand limit does not equal the function value, \(G\) is discontinuous at \(x=0\). 3. A function must be differentiable at every point of an interval to be an antiderivative there, and differentiability implies continuity. 4. Although \(G'(x)=g(x)\) for \(x\ne0\), \(G\) is not differentiable at \(x=0\). Therefore, \(G\) is not an antiderivative of \(g\) on \(\mathbb{R}\).

Answer

No. \(G\) is discontinuous, and therefore not differentiable, at \(x=0\).
Antiderivatives and indefinite integrals 107
The graph of a cubic polynomial \(f\) is shown. a) The function has the form \(f(x)=a(x-x_1)^2(x-x_2)\). Use the graph to determine \(a\), \(x_1\), and \(x_2\). b) Find the antiderivative \(F\) whose graph passes through \(A(2, 0)\). c) Classify the special point on the graph of \(F\) at \(x=2\). Which feature of \(f\) supports your classification?
Figure for problem 534428

Hints

- Distinguish between a zero where the graph crosses the x-axis and a zero where it only touches. - Use the y-intercept to determine \(a\). - Integrate term by term and use the given point to find the constant. - A zero of \(f\) without a sign change gives \(F\) a horizontal tangent but not an extremum.

Solution

1. The graph touches the x-axis at \(x=2\), so \(x_1=2\) is a double zero. It crosses at \(x=-1\), so \(x_2=-1\). Since \(f(0)=-2\), \(-2=a(0-2)^2(0+1)=4a\), giving \(a=-\frac12\). Thus, \(f(x)=-\frac12(x-2)^2(x+1)=-\frac12x^3+\frac32x^2-2\). 2. Integrating gives \(F(x)=-\frac18x^4+\frac12x^3-2x+C\). The condition \(F(2)=0\) gives \(-2+4-4+C=0\), so \(C=2\). Therefore, \(F(x)=-\frac18x^4+\frac12x^3-2x+2\). 3. Since \(f(2)=F^{\prime}(2)=0\), the graph of \(F\) has a horizontal tangent at \(x=2\). The function \(f\) does not change sign there, so \(F\) does not have a local extremum. Because \(f\) has a local maximum at \(x=2\), \(F\) changes concavity there. Thus, \(F\) has a stationary inflection point at \(x=2\).

Answer

a) \(a=-\frac12\), \(x_1=2\), \(x_2=-1\); \(f(x)=-\frac12x^3+\frac32x^2-2\) b) \(F(x)=-\frac18x^4+\frac12x^3-2x+2\) c) A stationary inflection point at \(x=2\); \(f\) has a zero without a sign change and a local maximum there.
Antiderivatives and indefinite integrals 108
Find constants \(a\), \(b\), and \(c\) such that \(\frac{\text{d}}{\text{d}x}\left[e^{2x}(ax^2+bx+c)\right]=e^{2x}(3x^2-4x+5)\). Then use your result to evaluate \(\int e^{2x}(3x^2-4x+5)\,\text{d}x\).

Hints

- Differentiate the entire product before comparing it with the given expression. - Organize the result by powers of the variable. - The coefficients of matching powers must agree.

Solution

1. Differentiate the proposed product to obtain \(e^{2x}[2ax^2+(2b+2a)x+(2c+b)]\). 2. Match coefficients with \(e^{2x}(3x^2-4x+5)\): \(2a=3\), \(2b+2a=-4\), and \(2c+b=5\). 3. Solving gives \(a=\frac{3}{2}\), \(b=-\frac{7}{2}\), and \(c=\frac{17}{4}\). 4. Therefore the integral is \(e^{2x}\left(\frac{3}{2}x^2-\frac{7}{2}x+\frac{17}{4}\right)+C\).

Answer

\(a=\frac{3}{2}\), \(b=-\frac{7}{2}\), and \(c=\frac{17}{4}\) \(\int e^{2x}(3x^2-4x+5)\,\text{d}x=e^{2x}\left(\frac{3}{2}x^2-\frac{7}{2}x+\frac{17}{4}\right)+C\)

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