Aimathic
Login | English | Deutsch

Free math worksheets

Build your own math worksheets from 30,000+ problems for grades 3 to 12, from fractions to AP Calculus. Every problem comes with step-by-step solutions.

Constant, sum, and difference rules

Click problems to add them to your worksheet.

55177912
Suppose \(f'(3)=2\). Define \(h(x)=4f(x)-7\). Find \(h'(3)\).

Hints

- Differentiate the constant multiple without needing a formula for \(f\). - A constant term contributes zero to the derivative. - Use the supplied derivative value only after applying the rule.

Solution

1. By the constant-multiple and constant rules, \(h'(x)=4f'(x)\). 2. Therefore, \(h'(3)=4\cdot2=8\).

Answer

\(h'(3)=8\)
55178012
Suppose \(u'(2)=3\) and \(v'(2)=-5\). If \(h(x)=u(x)+v(x)\), find \(h'(2)\).

Hints

- The derivative of a sum is the sum of the derivatives. - The original function values are not needed for this calculation. - Keep the sign of the second derivative value when combining them.

Solution

1. By the sum rule, \(h'(x)=u'(x)+v'(x)\). 2. Thus, \(h'(2)=3+(-5)=-2\).

Answer

\(h'(2)=-2\)
52226712
Cédric makes this conjecture: “If \(f(x)=g(x)+h(x)\), then \(f'(x)=g'(x)h'(x)\).” Refute the conjecture by stating the correct derivative rule and using \(g(x)=x^3\) and \(h(x)=x^2\) as a counterexample.

Hints

- What is the derivative rule for a sum? - Differentiate the two functions separately. - Compare the sum of the derivatives with their product. - Evaluate both expressions at a simple input to show they are different.

Solution

1. The correct sum rule is \(f'(x)=g'(x)+h'(x)\). 2. For the example, \(g'(x)=3x^2\) and \(h'(x)=2x\). 3. Therefore, the correct derivative is \(f'(x)=3x^2+2x\). 4. Cédric's rule would give \(g'(x)h'(x)=(3x^2)(2x)=6x^3\). 5. These expressions are not equal in general. For example, at \(x=1\), they give \(5\) and \(6\), respectively.

Answer

The conjecture is false. The sum rule gives \(f'(x)=g'(x)+h'(x)\). For the example, the correct derivative is \(3x^2+2x\), while the product of the derivatives is \(6x^3\).
52226812
Akira says: “To differentiate \(f(x)=5x^4\), I differentiate the constant \(5\) to get \(0\), so \(f'(x)=0(4x^3)=0\).” Explain the error and find the correct derivative.

Hints

- Distinguish multiplication from addition. - What does the constant-multiple rule say? - What happens to a constant coefficient multiplying a power of \(x\)? - Could the graph of \(5x^4\) have slope \(0\) everywhere?

Solution

1. Akira is confusing a constant term with a constant factor. The number \(5\) multiplies the variable expression; it is not a separate constant term. 2. By the constant-multiple rule, a constant factor remains: \(\frac{d}{dx}[c\,g(x)]=c\,g'(x)\). 3. Since \(\frac{d}{dx}(x^4)=4x^3\), the derivative is \(f'(x)=5(4x^3)=20x^3\).

Answer

Akira incorrectly differentiated a constant factor as though it were a separate constant term. The correct derivative is \(f'(x)=20x^3\).
52896312
The derivative of a constant function \(f(x)=c\) is \(f'(x)=0\). 1) For \(x\neq0\), rewrite \(f(x)=1\) as a power of \(x\). 2) Apply the power rule \(\frac{d}{dx}(x^n)=nx^{n-1}\) to that power. 3) Explain why the result agrees with the constant rule, and state the restriction on \(x\) in this power-rule argument.

Hints

- Recall the meaning of a zero exponent. - What happens when an expression is multiplied by \(0\)? - Is \(x^{-1}\) defined at every real value of \(x\)?

Solution

1. For \(x\neq0\), \(1=x^0\). 2. Applying the power rule with \(n=0\) gives \(\frac{d}{dx}(x^0)=0x^{-1}=0\) for \(x\neq0\). 3. This agrees with the constant rule. The power-rule expression \(x^{-1}\) is undefined at \(x=0\), so this particular argument does not apply there. However, the original constant function is differentiable at \(0\), and its derivative there is also \(0\).

Answer

1) \(f(x)=x^0\) for \(x\neq0\) 2) \(f'(x)=0x^{-1}=0\) for \(x\neq0\) 3) The power-rule argument excludes \(x=0\), but the constant function itself still satisfies \(f'(0)=0\).
52898912
Find \(f'(x)\) for each function. State the domain of each derivative. a) \(f(x)=\frac{6}{x}+4x^5-3\sin x\) b) \(f(x)=10\sqrt{x}-\frac{1}{2}\cos x+12\) c) \(f(x)=k\sin x+\frac{2}{x}\), where \(k\in\mathbb{R}\) is constant.

Hints

- Rewrite reciprocals and square roots as powers. - Differentiate each term separately. - Treat \(k\) as a constant. - Check where the original expressions and their derivatives are defined.

Solution

1. Differentiate each term in part a: \(\frac{d}{dx}(6x^{-1})=-6x^{-2}\), \(\frac{d}{dx}(4x^5)=20x^4\), and \(\frac{d}{dx}(-3\sin x)=-3\cos x\). Thus, \(f'(x)=-\frac{6}{x^2}+20x^4-3\cos x\), for \(x\ne0\). 2. For part b, \(\frac{d}{dx}(10x^{1/2})=5x^{-1/2}=\frac{5}{\sqrt{x}}\), \(\frac{d}{dx}\left(-\frac{1}{2}\cos x\right)=\frac{1}{2}\sin x\), and the derivative of \(12\) is \(0\). Therefore, \(f'(x)=\frac{5}{\sqrt{x}}+\frac{1}{2}\sin x\), for \(x>0\). 3. In part c, treat \(k\) as a constant: \(f'(x)=k\cos x-\frac{2}{x^2}\), for \(x\ne0\).

Answer

a) \(f'(x)=-\frac{6}{x^2}+20x^4-3\cos x\), for \(x\ne0\) b) \(f'(x)=\frac{5}{\sqrt{x}}+\frac{1}{2}\sin x\), for \(x>0\) c) \(f'(x)=k\cos x-\frac{2}{x^2}\), for \(x\ne0\)
52946712
Let \(f(x)=8\sin(x)\). Find \(f'(x)\) in two ways: 1. Use the constant multiple rule. 2. Use the product rule with \(u(x)=8\) and \(v(x)=\sin(x)\). Compare the methods. Why do they give the same result, and why is the constant multiple rule more efficient here?

Hints

- What is the derivative of a constant? - Substitute the two factors into the product rule. - What happens to the first product-rule term when one factor is constant? - Which method requires fewer steps?

Solution

1. By the constant multiple rule, \(f'(x)=8\cos(x)\). 2. Using the product rule, \(u'(x)=0\) and \(v'(x)=\cos(x)\), so \(f'(x)=u'(x)v(x)+u(x)v'(x)\) \(=0\sin(x)+8\cos(x)=8\cos(x)\). 3. The methods agree because the derivative of the constant factor is zero. The constant multiple rule is more efficient because it omits the product-rule term that equals zero.

Answer

1. \(f'(x)=8\cos(x)\) 2. \(f'(x)=8\cos(x)\). The product rule gives the same result because the derivative of \(8\) is \(0\); the constant multiple rule is more efficient because it avoids writing the zero product-rule term.
53374712
Let \(f(x)=x^3-3x^2+3x\). Verify algebraically that the graph has a horizontal tangent at \(x=1\).

Hints

- Differentiate the polynomial term by term. - Evaluate the derivative at the specified input. - Compare the result with the slope of a horizontal line.

Solution

1. Differentiate term by term: \(f'(x)=3x^2-6x+3\). 2. Evaluate at \(x=1\): \(f'(1)=0\). 3. Since a horizontal tangent has slope \(0\), the graph has a horizontal tangent at \(x=1\).

Answer

\(f'(x)=3x^2-6x+3\) and \(f'(1)=0\), so the tangent is horizontal at \(x=1\).
53374812
Let \(f(x)=\frac{1}{x}+x\) for \(x>0\). Verify algebraically that it has a horizontal tangent at \(x_0=1\), and find the point of tangency.

Hints

- Rewrite the reciprocal using a negative exponent. - Differentiate both terms and evaluate at \(x=1\). - Use the original function, not the derivative, for the y-coordinate.

Solution

1. Rewrite \(f(x)=x^{-1}+x\). Then \(f'(x)=-x^{-2}+1=-\frac{1}{x^2}+1\). 2. Since \(f'(1)=0\), the tangent is horizontal at \(x=1\). 3. The original function gives \(f(1)=2\), so the point of tangency is \((1,2)\).

Answer

\(f'(x)=-\frac{1}{x^2}+1\), \(f'(1)=0\), and the point of tangency is \((1,2)\).
53387112
Let \(f(x)=0.5x^2-2x+1\). Find an equation of the tangent line \(t\) to the graph of \(f\) at \(x_0=3\).

Hints

- Evaluate the original function to locate the point of tangency. - Differentiate the polynomial term by term for the tangent slope. - Use point-slope form to write the line.

Solution

1. The point of tangency is \((3,-0.5)\). 2. Differentiate term by term: \(f'(x)=x-2\), so the tangent slope is \(f'(3)=1\). 3. Using point-slope form, \(y+0.5=x-3\), so \(y=x-3.5\).

Answer

\(t:y=x-3.5\)
53417512
For \(f(x)=2x^2-3x\), use derivative rules to find the instantaneous rate of change at \(x=1\).

Hints

- Apply the Power Rule to the quadratic term. - Keep the constant factor attached to each differentiated term. - Evaluate only after finding the derivative function.

Solution

1. Differentiate term by term: \(f'(x)=4x-3\). 2. Evaluate the derivative: \(f'(1)=1\). 3. The instantaneous rate of change at \(x=1\) is \(1\).

Answer

\(f'(1)=1\)
53417612
Let \(g(x)=x^3-4x^2+2\). Find the slope of the graph at \(x=2\).

Hints

- Differentiate each term separately. - The derivative of the constant term is \(0\). - Substitute \(x=2\) only after differentiating.

Solution

1. Differentiate term by term: \(g'(x)=3x^2-8x\). 2. Evaluate at \(x=2\): \(g'(2)=12-16=-4\). 3. The graph has slope \(-4\) at \(x=2\).

Answer

\(g'(2)=-4\)
55178112
Let \(p(x)=ax^3+2x\). Find \(a\) if \(p'(1)=11\).

Hints

- Differentiate each term while treating \(a\) as a constant coefficient. - Use the derivative value at the specified input to create an equation for \(a\). - Solve the resulting linear equation only after differentiation.

Solution

1. Differentiate using the constant-multiple and sum rules: \(p'(x)=3ax^2+2\). 2. Substitute \(x=1\): \(3a+2=11\). 3. Solving gives \(a=3\).

Answer

\(a=3\)
52222312
Let \(f(x)=-x^2+4x-2\). a) Find the derivative function \(f'(x)\). b) Find the point \(P(x_0,f(x_0))\) where the graph of \(f\) has a horizontal tangent. c) Find the point \(Q(q,f(q))\) where the slope of the graph is \(6\).

Hints

- Differentiate the polynomial term by term. - A horizontal tangent corresponds to a derivative value of \(0\). - For a prescribed slope, set the derivative equal to that slope. - Substitute each resulting x-coordinate into the original function to find the point.

Solution

1. Differentiate using the power, constant, and sum rules: \(f'(x)=-2x+4\). 2. A horizontal tangent has slope \(0\), so solve \(-2x_0+4=0\). This gives \(x_0=2\). 3. Evaluate the function: \(f(2)=2\). Therefore, \(P=(2,2)\). 4. For slope \(6\), solve \(-2q+4=6\). This gives \(q=-1\). 5. Evaluate the function: \(f(-1)=-7\). Therefore, \(Q=(-1,-7)\).

Answer

a) \(f'(x)=-2x+4\) b) \(P=(2,2)\) c) \(Q=(-1,-7)\)
52222512
Let \(f(x)=x^3-12x+5\). a) Find the slope of the graph at \(x=-1\) and at \(x=3\). b) Find all values of \(x\) where the slope of the graph is \(15\). c) Find the points on the graph where the tangent line is parallel to \(y=-9x+2\). d) Find an equation of the tangent line to the graph at \(S=(0,f(0))\).

Hints

- Begin by differentiating the original polynomial rather than using a supplied derivative. - Set the derivative equal to each required slope. - Parallel lines have equal slopes. - After finding an input, use the original function to recover the corresponding point.

Solution

1. Differentiate term by term: \(f'(x)=3x^2-12\). 2. Evaluate the derivative: \(f'(-1)=-9\) and \(f'(3)=15\). 3. For slope \(15\), solve \(3x^2-12=15\). Then \(x^2=9\), so \(x=-3\) or \(x=3\). 4. A line parallel to \(y=-9x+2\) must have slope \(-9\). Solving \(3x^2-12=-9\) gives \(x=-1\) or \(x=1\). Since \(f(-1)=16\) and \(f(1)=-6\), the points are \((-1,16)\) and \((1,-6)\). 5. At \(x=0\), \(f(0)=5\) and \(f'(0)=-12\). The tangent line is \(y=-12x+5\).

Answer

a) \(f'(-1)=-9\) and \(f'(3)=15\) b) \(x=-3\) and \(x=3\) c) \((-1,16)\) and \((1,-6)\) d) \(y=-12x+5\)
52222612
Let \(g(x)=\frac{1}{3}x^3+x^2-3x\). a) Find \(g'(-2)\) and \(g'(1)\). b) Find all values of \(x\) where the graph of \(g\) has slope \(5\). c) Find the points on the graph where the tangent line is parallel to \(y=-3x+10\).

Hints

- Differentiate the original polynomial term by term first. - Set the derivative equal to the requested slope and solve. - Read the comparison line's slope from its equation. - Substitute each relevant input into the original function to find the point.

Solution

1. Differentiate term by term: \(g'(x)=x^2+2x-3\). 2. Evaluate: \(g'(-2)=-3\) and \(g'(1)=0\). 3. For slope \(5\), solve \(x^2+2x-3=5\). Factoring \(x^2+2x-8=(x+4)(x-2)\) gives \(x=-4\) or \(x=2\). 4. A tangent parallel to \(y=-3x+10\) must have slope \(-3\). Solve \(x^2+2x-3=-3\), giving \(x=0\) or \(x=-2\). 5. Since \(g(0)=0\) and \(g(-2)=\frac{22}{3}\), the points are \((0,0)\) and \((-2,\frac{22}{3})\).

Answer

a) \(g'(-2)=-3\) and \(g'(1)=0\) b) \(x=-4\) and \(x=2\) c) \((0,0)\) and \((-2,\frac{22}{3})\)
52235312
Let \(f(x)=x^2+x+1\) and \(g(x)=-x^2+5x-1\). 1. Show algebraically that the graphs of \(f\) and \(g\) are tangent to each other at \(x=1\). 2. Find an equation of their common tangent line at that point.

Hints

- First verify that the two functions have the same value at \(x=1\). - Then compare their derivative values at that input. - A common tangent must share both the point and the slope.

Solution

1. The function values agree: \(f(1)=3\) and \(g(1)=3\), so both graphs pass through \((1,3)\). 2. Differentiate term by term: \(f'(x)=2x+1\) and \(g'(x)=-2x+5\). 3. The slopes also agree at \(x=1\): \(f'(1)=g'(1)=3\). Therefore, the graphs are tangent at \((1,3)\). 4. The common tangent line is \(y-3=3(x-1)\), so \(y=3x\).

Answer

1. Both graphs pass through \((1,3)\), and \(f'(1)=g'(1)=3\), so they are tangent there. 2. \(y=3x\)
52243512
Find an equation of the tangent line to \(f(x)=x^3-2x^2+1\) at \(P=(2,f(2))\). Also find the angle that the tangent line makes with the positive x-axis, to the nearest hundredth of a degree.

Hints

- Differentiate the polynomial term by term to obtain the tangent slope. - Use the original function to locate the point of tangency. - Write the line with point-slope form. - Relate slope to inclination with the tangent function and use the requested precision.

Solution

1. Find the point of tangency: \(f(2)=1\), so \(P=(2,1)\). 2. Differentiate term by term: \(f'(x)=3x^2-4x\). 3. The tangent slope is \(f'(2)=4\). 4. The tangent line is \(y-1=4(x-2)\), or \(y=4x-7\). 5. The angle \(\alpha\) satisfies \(\tan(\alpha)=4\), so \(\alpha=\arctan(4)\approx75.96^\circ\).

Answer

Tangent line: \(y=4x-7\) Angle: \(\alpha\approx75.96^\circ\)
52742312
Let \(f(x)=\frac{(3x-2)^2}{2x}\). a) Find an equation of the tangent line to the graph at \(P=(1,0.5)\). b) Identify the vertical asymptote of \(f'\), and determine whether \(f'\) changes sign when crossing that asymptote sufficiently close to it.

Hints

- Simplify the rational expression before differentiating. - Use the derivative value at \(x=1\) as the tangent slope. - For the asymptote, identify where the derivative denominator is zero while the numerator is nonzero. - For the sign question, analyze the numerator and denominator only near \(x=0\).

Solution

1. Simplify before differentiating: \(f(x)=4.5x-6+\frac{2}{x}\). 2. Differentiate term by term: \(f'(x)=4.5-\frac{2}{x^2}=\frac{9x^2-4}{2x^2}\). 3. At \(x=1\), the slope is \(f'(1)=2.5\). Through \((1,0.5)\), the tangent is \(y-0.5=2.5(x-1)\), so \(y=2.5x-2\). 4. The derivative is undefined at \(x=0\), and its numerator approaches \(-4\ne0\), so \(x=0\) is a vertical asymptote of \(f'\). For \(x\) sufficiently close to \(0\), \(9x^2-4<0\) while \(2x^2>0\), so \(f'(x)<0\) on both sides. Thus, there is no sign change across the asymptote sufficiently close to \(0\).

Answer

a) \(y=2.5x-2\) b) The vertical asymptote of \(f'\) is \(x=0\). The derivative is negative on both sides sufficiently close to the asymptote, so it does not change sign there.
52900312
Let \(f(x)=x^2-2x+2\) and \(g(x)=-x^2+4x-2\). 1. Find the intersection points of the two graphs. 2. Find the acute angle at which the graphs intersect at each point, to the nearest hundredth of a degree.

Hints

- Set the two function values equal to find the intersections. - Differentiate both polynomials term by term to obtain their tangent slopes. - Use the angle-between-lines formula for the two slopes at each intersection. - Round only the final angle to the requested precision.

Solution

1. Set the functions equal: \(x^2-2x+2=-x^2+4x-2\). This simplifies to \(x^2-3x+2=0\), so \(x=1\) or \(x=2\). The points are \((1,1)\) and \((2,2)\). 2. Differentiate term by term: \(f'(x)=2x-2\) and \(g'(x)=-2x+4\). 3. At \(x=1\), the slopes are \(0\) and \(2\). Thus, \(\tan(\gamma)=2\), so \(\gamma=\arctan(2)\approx63.43^\circ\). 4. At \(x=2\), the slopes are \(2\) and \(0\), giving the same acute angle, \(63.43^\circ\).

Answer

1. \((1,1)\) and \((2,2)\) 2. The acute intersection angle is approximately \(63.43^\circ\) at both points.
52900412
The graphs of \(f(x)=x^3-x\) and \(g(x)=x^2-1\) intersect at \(P=(-1,0)\) and \(Q=(1,0)\). Analyze the angle of intersection at each point. Give any nonzero angle to the nearest hundredth of a degree.

Hints

- Differentiate both functions term by term and evaluate the slopes at each intersection. - Equal tangent slopes give an intersection angle of \(0^\circ\). - Otherwise use the acute angle-between-lines formula and the requested precision.

Solution

1. Differentiate term by term: \(f'(x)=3x^2-1\) and \(g'(x)=2x\). 2. At \(P=(-1,0)\), the slopes are \(2\) and \(-2\). Therefore, \(\tan(\gamma)=\frac{4}{3}\), so \(\gamma=\arctan\!\left(\frac{4}{3}\right)\approx53.13^\circ\). 3. At \(Q=(1,0)\), both slopes equal \(2\). The tangent lines coincide, so the intersection angle is \(0^\circ\); the graphs are tangent at \(Q\).

Answer

At \(P=(-1,0)\), the acute intersection angle is approximately \(53.13^\circ\). At \(Q=(1,0)\), the angle is \(0^\circ\); the graphs are tangent there.
52901112
Let \(f(x)=x^2\) and \(g(x)=(x-2)^2\). a) Find the intersection point \(P\) of the two graphs. b) At \(P\), tangent lines are drawn to both graphs. Find the x-intercept of each tangent line. c) The two tangent lines and the x-axis form a triangle. Find its area.

Hints

- Set the function values equal to locate the common point. - Expand the translated square before differentiating so only the rules from this topic are needed. - Find each tangent line from its point and slope, then set \(y=0\) for the x-intercepts. - Use the x-axis segment as the triangle's base.

Solution

1. Set the functions equal: \(x^2=(x-2)^2\). This gives \(x=1\), and the common value is \(1\), so \(P=(1,1)\). 2. Expand \(g(x)=x^2-4x+4\). Then \(f'(x)=2x\) and \(g'(x)=2x-4\) by the rules available in this topic. At \(x=1\), the slopes are \(2\) and \(-2\). 3. The tangent lines are \(y=2x-1\) and \(y=-2x+3\). 4. Their x-intercepts are \(\left(\frac{1}{2},0\right)\) and \(\left(\frac{3}{2},0\right)\). 5. The base on the x-axis has length \(1\), and the height from \(P\) is \(1\), so the area is \(\frac{1}{2}\) square unit.

Answer

a) \(P=(1,1)\) b) \(\left(\frac{1}{2},0\right)\) and \(\left(\frac{3}{2},0\right)\) c) \(\frac{1}{2}\) square unit
53242512
The graphs of \(f(x)=x^2-6x+9\) and \(g(x)=-x+5\) intersect at two points, \(P_1\) and \(P_2\). Let \(P_1\) be the point with the smaller x-coordinate. The angle of intersection of two graphs is the acute angle formed by their tangent lines at the intersection point. a) Find the coordinates of \(P_1\) and \(P_2\). b) Find the slopes of the tangent lines to the graphs of \(f\) and \(g\) at each intersection point. c) Find the angles of intersection \(\alpha_1\) at \(P_1\) and \(\alpha_2\) at \(P_2\). Give each answer in degrees to the nearest hundredth.

Hints

- Set the two function expressions equal to locate the intersections. - Differentiate both formulas term by term to obtain tangent slopes. - Use the acute-angle formula only after the two slopes at each intersection are known.

Solution

1. Set the functions equal: \(x^2-6x+9=-x+5\). Then \(x^2-5x+4=0\), so \(x=1\) or \(x=4\). Thus, \(P_1=(1,4)\) and \(P_2=(4,1)\). 2. Differentiate term by term: \(f'(x)=2x-6\) and \(g'(x)=-1\). At \(P_1\), the slopes are \(-4\) and \(-1\). At \(P_2\), the slopes are \(2\) and \(-1\). 3. Using \(\tan(\alpha)=\left|\frac{m_1-m_2}{1+m_1m_2}\right|\), at \(P_1\), \(\tan(\alpha_1)=0.6\), so \(\alpha_1\approx30.96^\circ\). 4. At \(P_2\), \(\tan(\alpha_2)=3\), so \(\alpha_2\approx71.57^\circ\).

Answer

a) \(P_1=(1,4)\) and \(P_2=(4,1)\) b) At \(P_1\), the slopes are \(-4\) for \(f\) and \(-1\) for \(g\). At \(P_2\), the slopes are \(2\) for \(f\) and \(-1\) for \(g\). c) \(\alpha_1\approx30.96^\circ\) and \(\alpha_2\approx71.57^\circ\)
53242812
Let \(f(x)=-0.25x^2+x+3\). The point \(Q=(0,7)\) lies above the graph of \(f\). Two tangent lines to the graph pass through \(Q\). a) Find the coordinates of the two points of tangency, \(B_1\) and \(B_2\). b) Find equations of the two tangent lines, \(t_1\) and \(t_2\).

Hints

- Write the tangent-line equation at a general input \(u\). - A tangent through \(Q\) must produce the point's y-value when \(x=0\). - Solve the resulting equation for the possible tangency inputs. - Use each input in the original function and derivative to finish the tangent line.

Solution

1. The tangent line at \(x=u\) is \(t(x)=f'(u)(x-u)+f(u)\), with \(f'(x)=-0.5x+1\). 2. Requiring \(t(0)=7\) gives \((-0.5u+1)(-u)-0.25u^2+u+3=7\), which simplifies to \(0.25u^2=4\). Thus, \(u=4\) or \(u=-4\). 3. Since \(f(4)=3\) and \(f(-4)=-5\), the tangency points are \(B_1=(4,3)\) and \(B_2=(-4,-5)\). 4. The corresponding slopes are \(-1\) and \(3\), so the tangent lines are \(y=-x+7\) and \(y=3x+7\).

Answer

a) \(B_1=(4,3)\) and \(B_2=(-4,-5)\) b) \(t_1:y=-x+7\) and \(t_2:y=3x+7\)
53266112
The functions are \(f(x)=0.5x^2-2\) and \(g(x)=-0.2x^3+1.5x\). The four figures show \(f\), \(g\), \(f'\), and \(g'\) in random order. a) Compute \(f'(x)\) and \(g'(x)\) using the Power Rule together with the constant-multiple and sum/difference rules. b) Match graphs (1) through (4) with \(f\), \(g\), \(f'\), and \(g'\). c) Give one derivative-based graphical check for each matched function-derivative pair.
Figure for problem 532661

Hints

- Compute both derivatives before matching any panels. - Use the formulas you obtained to identify the line and parabola representing the derivatives. - Confirm each pairing by comparing derivative zeros with horizontal tangents of the original graph.

Solution

1. Differentiate term by term: \(f'(x)=x\) and \(g'(x)=-0.6x^2+1.5\). 2. Graph (3) is the upward-opening parabola with vertex \((0,-2)\), so it represents \(f\). Graph (1) is the line \(y=x\), so it represents \(f'\). 3. Graph (2) is the odd cubic with negative leading coefficient, so it represents \(g\). Graph (4) is the downward-opening parabola with y-intercept \(1.5\), so it represents \(g'\). 4. The zero of graph (1) at \(x=0\) matches the horizontal tangent of graph (3) there. The zeros of graph (4) align with the turning points of graph (2).

Answer

a) \(f'(x)=x\); \(g'(x)=-0.6x^2+1.5\) b) (1) \(f'\); (2) \(g\); (3) \(f\); (4) \(g'\) c) The derivative zeros align with horizontal tangents of their corresponding function graphs.
53277812
Let \(f(x)=-0.25x^2+4\). a) Find the x-intercepts \(P\) and \(Q\) of the graph. b) Find equations of the tangent lines \(t_1\) and \(t_2\) at \(P\) and \(Q\), respectively. c) The tangent lines intersect at \(S\). Find the area of triangle \(PQS\).

Hints

- Set the function equal to zero to find the x-intercepts. - Use the derivative for each tangent slope. - Solve the two tangent equations together to locate \(S\). - Use \(\overline{PQ}\) as the triangle's base.

Solution

1. Set \(f(x)=0\): \(-0.25x^2+4=0\), so \(x=\pm4\). Thus, \(P=(-4,0)\) and \(Q=(4,0)\). 2. Differentiate: \(f'(x)=-0.5x\). At \(P\), the slope is \(2\), so \(t_1:y=2x+8\). At \(Q\), the slope is \(-2\), so \(t_2:y=-2x+8\). 3. Solving the tangent equations together gives \(S=(0,8)\). 4. Triangle \(PQS\) has base \(8\) and height \(8\), so its area is \(32\) square units.

Answer

a) \(P=(-4,0)\) and \(Q=(4,0)\) b) \(t_1:y=2x+8\) and \(t_2:y=-2x+8\) c) \(32\) square units
53380612
Let \(f(x)=x^2-2x\), \(g(x)=f(x)+3\), and \(h(x)=f(x+2)\). The four figures show \(f\), \(f'\), \(g\), and \(h\) in random order. a) Compute \(f'(x)\) using the Power Rule together with the constant-multiple and difference rules. b) Match \(f\), \(f'\), \(g\), and \(h\) with graphs I through IV. c) Explain one visual feature that confirms your identification of the graph of \(f'\).
Figure for problem 533806

Hints

- Differentiate \(f\) before trying to match the panels. - Use the computed derivative formula to identify the linear panel. - Then use vertical and horizontal translations to distinguish \(g\) and \(h\). - Check that a zero of the derivative aligns with a horizontal tangent of \(f\).

Solution

1. Differentiate term by term: \(f'(x)=2x-2\). 2. The graph of \(f\) is an upward-opening parabola with zeros at \(0\) and \(2\) and vertex \((1,-1)\), so it is graph II. 3. The derivative \(f'(x)=2x-2\) is a line with zero at \(x=1\), so it is graph IV. Its zero aligns with the horizontal tangent at the vertex of graph II. 4. The graph of \(g=f+3\) is shifted up \(3\) units and has vertex \((1,2)\), so it is graph I. 5. The graph of \(h(x)=f(x+2)\) is shifted left \(2\) units and has vertex \((-1,-1)\), so it is graph III.

Answer

a) \(f'(x)=2x-2\) b) Graph I: \(g\); Graph II: \(f\); Graph III: \(h\); Graph IV: \(f'\) c) Graph IV crosses the x-axis at \(x=1\), the x-coordinate of the horizontal tangent at the vertex of graph II.
53392012
The graphs of \(f\) and \(g\) satisfy \(g(x)=kf(x)\). 1. Use the function values at \(x=4\) to find the scale factor \(k\). 2. Use the drawn tangent segments to find \(f'(4)\) and \(g'(4)\). 3. Compare the ratio of the slopes with the scale factor \(k\). What derivative rule does this illustrate?
Figure for problem 533920

Hints

- Read both y-values at \(x=4\). - Use the actual endpoints of each drawn tangent segment to compute rise over run. - Compare the slope ratio with the function-value scale factor.

Solution

1. From the graph, \(f(4)=2\) and \(g(4)=4\). Since \(g(4)=kf(4)\), \(4=2k\), so \(k=2\). 2. The tangent to \(f\) rises \(4\) units over a run of \(4\), so \(f'(4)=1\). The tangent to \(g\) rises \(6\) units over a run of \(3\), so \(g'(4)=2\). 3. Therefore, \(g'(4)=2f'(4)=kf'(4)\). This illustrates the constant multiple rule: if \(g(x)=kf(x)\), then \(g'(x)=kf'(x)\).

Answer

1. \(k=2\) 2. \(f'(4)=1\) and \(g'(4)=2\) 3. \(g'(4)=kf'(4)\), illustrating the constant multiple rule.
53392312
Let \(f(x)=x^2-1\) and \(g(x)=7-x^2\). Their graphs intersect at two points. a) Find the coordinates of both intersection points. b) Find the acute angle at which the graphs intersect at each point, to the nearest tenth of a degree.

Hints

- Set the two function expressions equal to locate the intersections. - Differentiate both polynomials to obtain tangent slopes. - Use the acute angle-between-lines formula and round only the final angle.

Solution

1. Set the functions equal: \(x^2-1=7-x^2\), giving \(x=\pm2\). The intersection points are \((2,3)\) and \((-2,3)\). 2. Differentiate: \(f'(x)=2x\) and \(g'(x)=-2x\). At \(x=2\), the tangent slopes are \(4\) and \(-4\). 3. Thus, \(\tan(\phi)=\left|\frac{4-(-4)}{1+4(-4)}\right|=\frac{8}{15}\), so \(\phi\approx28.1^\circ\). 4. By symmetry, the acute angle at the other intersection is also \(28.1^\circ\).

Answer

a) \((2,3)\) and \((-2,3)\) b) The angle at each intersection is approximately \(28.1^\circ\).
53422612
Let \(f(x)=-0.5x^2+3x\). a) Find \(f'(x)\). b) Find the point \(S\) where the graph of \(f\) has a horizontal tangent. c) At what x-value is the tangent line parallel to \(y=x\)? Give the corresponding point \(R\).

Hints

- Differentiate the polynomial term by term. - A horizontal tangent has slope \(0\). - A tangent parallel to \(y=x\) must have slope \(1\). - Substitute each solved input into \(f\) to recover the point.

Solution

1. Differentiate term by term: \(f'(x)=-x+3\). 2. For a horizontal tangent, solve \(-x+3=0\), giving \(x=3\). Since \(f(3)=4.5\), \(S=(3,4.5)\). 3. The line \(y=x\) has slope \(1\). Solve \(-x+3=1\), giving \(x=2\). Since \(f(2)=4\), \(R=(2,4)\).

Answer

a) \(f'(x)=-x+3\) b) \(S=(3,4.5)\) c) \(x=2\), and \(R=(2,4)\)
53424212
Let \(f(x)=\frac{1}{2}x^2+2\). For each \(a\in\mathbb{R}\), let \(Q_a=(a,f(a))\), and let \(P=(0,0)\). a) For \(a\ne0\), find the slope \(m_a\) of the secant line through \(P\) and \(Q_a\) in terms of \(a\). b) Let \(t_a\) be the tangent line to \(f\) at \(Q_a\). Find every value of \(a\) for which \(t_a\) passes through \(P\).

Hints

- Use the slope formula between \(P\) and the parameterized point \(Q_a\). - The derivative at \(a\) gives the tangent slope. - Write the tangent line in terms of \(a\), then impose the condition that it passes through \(P\).

Solution

1. Since \(Q_a=\left(a,\frac{1}{2}a^2+2\right)\), the secant slope is \(m_a=\frac{a^2+4}{2a}\). 2. Differentiate: \(f'(x)=x\). 3. The tangent at \(Q_a\) is \(y=a(x-a)+\frac{1}{2}a^2+2=ax-\frac{1}{2}a^2+2\). 4. For this line to pass through \(P=(0,0)\), \(0=-\frac{1}{2}a^2+2\). Thus, \(a=2\) or \(a=-2\).

Answer

a) \(m_a=\frac{a^2+4}{2a}\) b) \(a=2\) and \(a=-2\)
53486012
A quadratic function \(f\) crosses the x-axis at the origin and at \(x=4\). The tangent lines at these two intercepts meet at \(S=(2,-6)\). Find \(f(x)\).

Hints

- Use the factored form of a quadratic with the two given zeros. - Differentiate that form after expanding it. - Write the tangent line through the origin using its derivative slope. - Use the given intersection point of the tangents to determine the remaining coefficient.

Solution

1. Since the zeros are \(0\) and \(4\), write \(f(x)=ax(x-4)=ax^2-4ax\). 2. Differentiate: \(f'(x)=2ax-4a\). At the origin, the tangent slope is \(-4a\), so the tangent line there is \(y=-4ax\). 3. Since \(S=(2,-6)\) lies on this tangent, \(-6=-8a\), so \(a=\frac{3}{4}\). 4. Therefore, \(f(x)=\frac{3}{4}x^2-3x\).

Answer

\(f(x)=\frac{3}{4}x^2-3x\)
55178212
The figure shows \(u\), \(v\), and the tangent line \(t\) to \(u\) at \(x=1\). Define \(w(x)=u(x)-v(x)\). Use the graph to find \(w'(1)\).
Figure for problem 551782

Hints

- Read the derivative of \(u\) from its tangent line at the marked input. - Because \(v\) is a line, its derivative is its constant slope. - Apply the difference rule after obtaining the two component slopes.

Solution

1. The tangent line \(t\) to \(u\) passes through grid points \((0.5,0)\) and \((1,1)\), so \(u'(1)=\frac{1-0}{1-0.5}=2\). 2. The graph of \(v\) is a line with slope \(-1\), so \(v'(1)=-1\). 3. By the difference rule, \(w'(1)=u'(1)-v'(1)=2-(-1)=3\).

Answer

\(w'(1)=3\)
53253612
Let \(f(x)=0.5x^3-1.5x\). The point \(P=(2,-3)\) does not lie on the graph of \(f\). Tangent lines drawn from \(P\) touch the graph at points \(Q_a=(a,f(a))\). a) Write the equation of the tangent line \(t_a\) at \(Q_a\) in terms of \(a\). b) Find every value of \(a\) for which \(t_a\) passes through \(P\), and give the equations of those tangent lines.

Hints

- Differentiate the polynomial and write the tangent equation at a general input \(a\). - Substitute the coordinates of \(P\) into that general line. - Factor the resulting equation in \(a\).

Solution

1. Differentiate term by term: \(f'(x)=1.5x^2-1.5\). 2. The tangent at \(x=a\) is \(t_a(x)=f'(a)(x-a)+f(a)\), which simplifies to \(t_a(x)=(1.5a^2-1.5)x-a^3\). 3. Requiring the tangent to pass through \(P=(2,-3)\) gives \(-3=2(1.5a^2-1.5)-a^3\), or \(a^2(3-a)=0\). 4. Thus, \(a=0\) or \(a=3\). The tangent lines are \(t_0(x)=-1.5x\) and \(t_3(x)=12x-27\).

Answer

a) \(t_a(x)=(1.5a^2-1.5)x-a^3\) b) \(a=0\) gives \(t_0(x)=-1.5x\), and \(a=3\) gives \(t_3(x)=12x-27\).

All problems may be used, copied and printed free of charge for school and tutoring, including paid tutoring. Commercial adaptations as well as publication or redistribution on the internet are not permitted.