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Integration by substitution

Learning goals

  • Identifies an inner expression and corresponding differential factor.
  • Performs a valid substitution.
  • Integrates in the new variable and back-substitutes when needed.
  • Converts integration bounds to the substituted variable.
  • Checks by differentiation where practical.

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Integration by substitution 1
Consider \(\int 6x(x^2+4)^5\,\text{d}x\). Choose a substitution that turns the integral into a constant multiple of \(\int u^5\,\text{d}u\). State \(u\), \(\text{d}u\), and the transformed integral, but do not evaluate it.

Hints

- Look for the repeated inner expression that is raised to a power. - Check whether its derivative accounts for the remaining factor outside that power. - After substitution, no \(x\) should remain in the transformed integral.

Solution

1. Choose the inner expression \(u=x^2+4\). 2. Then \(\text{d}u=2x\,\text{d}x\), so \(6x\,\text{d}x=3\,\text{d}u\). 3. The power becomes \(u^5\), giving \(3\int u^5\,\text{d}u\).

Answer

\(u=x^2+4\), \(\text{d}u=2x\,\text{d}x\), and the transformed integral is \(3\int u^5\,\text{d}u\).
Integration by substitution 2
In \(\int 2x\cos(x^2+1)\,\text{d}x\), which expression should be replaced by \(u\), and which factor is its derivative?

Hints

- Look for an expression inside another function. - Differentiate that inner expression. - Check whether its derivative appears elsewhere in the integrand.

Solution

1. The inner expression is \(x^2+1\), so set \(u=x^2+1\). 2. Its derivative is \(2x\), and \(\text{d}u=2x\,\text{d}x\). This factor is already present in the integral.

Answer

\(u=x^2+1\), with \(\text{d}u=2x\,\text{d}x\)
Integration by substitution 3
In \(\int 3(5x+2)^4\,\text{d}x\), use \(u=5x+2\). What constant factor must appear in front of \(\int u^4\,\text{d}u\)? Do not finish the integration.

Hints

- Differentiate the expression chosen for \(u\). - Solve the differential relationship for \(\text{d}x\). - Include the coefficient already multiplying the power.

Solution

1. Differentiating the substitution gives \(\text{d}u=5\,\text{d}x\), so \(\text{d}x=\frac15\,\text{d}u\). 2. The original factor \(3\) becomes \(\frac35\), giving \(\frac35\int u^4\,\text{d}u\).

Answer

\(\frac35\)
Integration by substitution 4
A student claims \(\int 2x e^{x^2}\,\text{d}x=2e^{x^2}+C\). Check the claim by differentiating and give a correct antiderivative.

Hints

- Differentiate the proposed answer using the chain rule. - Compare its coefficient with the original integrand. - Adjust the constant factor rather than changing the exponent.

Solution

1. The derivative of \(2e^{x^2}\) is \(4x e^{x^2}\), twice the integrand, so the claim is false. 2. A correct antiderivative is \(e^{x^2}+C\), whose derivative is \(2x e^{x^2}\).

Answer

The claim is false: its derivative is \(4xe^{x^2}\). A correct antiderivative is \(e^{x^2}+C\).
Integration by substitution 5
For \(\int_1^3\frac{2x}{x^2+1}\,\text{d}x\), let \(u=x^2+1\). What are the new lower and upper limits? Do not evaluate the integral.

Hints

- Substitute each original x-limit into the expression for \(u\). - Keep the original lower and upper limits in their respective positions.

Solution

1. When \(x=1\), the new variable is \(u=1^2+1=2\). 2. When \(x=3\), it is \(u=3^2+1=10\).

Answer

Lower limit \(2\); upper limit \(10\)
Integration by substitution 6
Evaluate the definite integral using an appropriate integration rule: \(\int_{0}^{1}\frac{6x^2+2}{x^3+x+1} \, dx\).

Hints

- Compare the numerator with the derivative of the denominator. - Try a substitution using the denominator. - Recall the antiderivative of \(\frac{1}{u}\). - When using substitution in a definite integral, update the limits or substitute back before evaluating.

Solution

1. Let \(u=x^3+x+1\). Then \(du=(3x^2+1)\,dx\), and \((6x^2+2)\,dx=2\,du\). 2. Change the limits: when \(x=0\), \(u=1\); when \(x=1\), \(u=3\). 3. The integral becomes \(2\int_1^3 \frac{1}{u}\,du=2[\ln|u|]_1^3=2\ln(3)-2\ln(1)=2\ln(3)\).

Answer

\(2\ln(3)\)
Integration by substitution 7
Evaluate the integral using substitution or by recognizing a composite function: \(\int_{0}^{\pi} \sin(x)e^{\cos(x)} \, dx\).

Hints

- Compare the factor outside the exponential with the derivative of its exponent. - What substitution uses the exponent of \(e\)? - Remember the negative sign in the derivative of cosine. - Update the limits after making a substitution in a definite integral.

Solution

1. Let \(u=\cos(x)\), so \(du=-\sin(x)\,dx\). 2. Change the limits: when \(x=0\), \(u=1\); when \(x=\pi\), \(u=-1\). 3. Then \(\int_0^\pi \sin(x)e^{\cos(x)}\,dx=-\int_1^{-1}e^u\,du=\int_{-1}^{1}e^u\,du\). 4. Evaluate: \([e^u]_{-1}^{1}=e-e^{-1}=e-\frac{1}{e}\).

Answer

\(e-\frac{1}{e}\)
Integration by substitution 8
Evaluate the integral using an appropriate substitution: \(\int_{1}^{2}\frac{e^{\frac{1}{x}}}{x^2} \, dx\).

Hints

- Use the exponent of \(e\) as a possible substitution. - Compare its derivative with the remaining factor in the integrand. - Update the limits after substituting. - A negative sign can be handled by reversing the new limits.

Solution

1. Let \(u=\frac{1}{x}\). Then \(du=-\frac{1}{x^2}\,dx\). 2. Change the limits: when \(x=1\), \(u=1\); when \(x=2\), \(u=\frac{1}{2}\). 3. The integral becomes \(-\int_1^{\frac{1}{2}}e^u\,du=\int_{\frac{1}{2}}^1e^u\,du\). 4. Evaluate: \([e^u]_{\frac{1}{2}}^1=e-e^{\frac{1}{2}}=e-\sqrt{e}\).

Answer

\(e-\sqrt{e}\)
Integration by substitution 9
Evaluate each definite integral using an appropriate integration rule. a) \(\int_{1}^{4}\frac{2x+1}{x^2+x} \, dx\) b) \(\int_{0}^{4}\sqrt{2x+1} \, dx\)

Hints

- In a), compare the numerator with the derivative of the denominator. - Recall the antiderivative associated with \(\frac{u'}{u}\). - In b), rewrite the square root using exponent \(\frac{1}{2}\). - Include the reciprocal of the inner derivative when integrating a linear composite function.

Solution

1. For a), let \(u=x^2+x\), so \(du=(2x+1)\,dx\). Then \(\int_1^4\frac{2x+1}{x^2+x}\,dx=[\ln(x^2+x)]_1^4=\ln(20)-\ln(2)=\ln(10)\). 2. For b), let \(u=2x+1\), so \(du=2\,dx\). Change the limits: \(x=0\) gives \(u=1\), and \(x=4\) gives \(u=9\): \(\int_0^4\sqrt{2x+1}\,dx=\frac{1}{2}\int_1^9u^{\frac{1}{2}}\,du\). 3. Evaluate: \(\frac{1}{2}[\frac{2}{3}u^{\frac{3}{2}}]_1^9=\frac{1}{3}(27-1)=\frac{26}{3}\).

Answer

a) \(\ln(10)\) b) \(\frac{26}{3}\)
Integration by substitution 10
Find one antiderivative for each function. a) \(f(x)=\frac{6x-9}{x^2-3x+10}\) b) \(g(t)=8\sin\left(\frac{t}{2}+\pi\right)\)

Hints

- In a), compare the numerator with the derivative of the denominator. - Recall the logarithmic antiderivative pattern. - In b), identify the derivative of the inner linear expression. - What function differentiates to sine, and how must the inner derivative be handled?

Solution

1. For a), the derivative of \(x^2-3x+10\) is \(2x-3\), and \(6x-9=3(2x-3)\). Therefore, \(F(x)=3\ln|x^2-3x+10|\). 2. For b), account for the inner derivative \(\frac{1}{2}\). Since an antiderivative of sine is negative cosine, \(G(t)=-16\cos\left(\frac{t}{2}+\pi\right)\).

Answer

a) \(F(x)=3\ln|x^2-3x+10|\) b) \(G(t)=-16\cos\left(\frac{t}{2}+\pi\right)\)
Integration by substitution 11
Find one antiderivative for each function. a) \(f(x)=xe^{1-x^2}\) b) \(h(x)=\frac{[\ln(x)]^2}{x}\), for \(x>0\)

Hints

- In a), compare the derivative of the exponent with the factor outside the exponential. - Look for a chain-rule pattern in each integrand. - In b), rewrite the expression as \([\ln(x)]^2\cdot\frac{1}{x}\). - Use the inner function as the substitution variable.

Solution

1. For a), let \(u=1-x^2\), so \(du=-2x\,dx\). Then \(\int xe^{1-x^2}\,dx=-\frac{1}{2}\int e^u\,du=-\frac{1}{2}e^{1-x^2}+C\). 2. For b), let \(u=\ln(x)\), so \(du=\frac{1}{x}\,dx\). Then \(\int\frac{[\ln(x)]^2}{x}\,dx=\int u^2\,du=\frac{1}{3}u^3+C=\frac{1}{3}[\ln(x)]^3+C\).

Answer

a) \(F(x)=-\frac{1}{2}e^{1-x^2}\) b) \(H(x)=\frac{1}{3}[\ln(x)]^3\)
Integration by substitution 12
Evaluate the definite integral using an appropriate integration rule: \(\int_{1}^{2}\frac{6x^2-2}{x^3-x+5} \, dx\).

Hints

- How are the numerator and denominator related? - Could a change of variable make the fraction easier to integrate? - If you change variables, what happens to the integration limits?

Solution

1. Let \(u=x^3-x+5\). Then \(du=(3x^2-1)\,dx\), and \((6x^2-2)\,dx=2\,du\). 2. Change the limits: when \(x=1\), \(u=5\); when \(x=2\), \(u=11\). 3. The integral becomes \(2\int_5^{11}\frac{1}{u}\,du=2[\ln|u|]_5^{11}\). 4. Therefore, the value is \(2\ln(11)-2\ln(5)=2\ln\left(\frac{11}{5}\right)\).

Answer

\(2\ln\left(\frac{11}{5}\right)\)
Integration by substitution 13
Evaluate the definite integral \(\int_{0}^{2}e^{1-0.5x} \, dx\).

Hints

- Identify the derivative of the linear exponent. - Reverse the chain rule to find an antiderivative. - Recall that \(e^0=1\). - Track the negative sign when evaluating the limits.

Solution

1. An antiderivative of \(e^{1-0.5x}\) is \(-2e^{1-0.5x}\), because the derivative of \(1-0.5x\) is \(-0.5\). 2. Evaluate at the limits: \([-2e^{1-0.5x}]_0^2=-2e^0-(-2e^1)\). 3. Simplify to obtain \(2e-2\).

Answer

\(2e-2\)
Integration by substitution 14
Evaluate each integral using an appropriate integration method. a) \(\int_{1}^{2}\frac{3x^2}{x^3+1} \, dx\) b) \(\int_{0}^{2}(2x-1)e^{x^2-x} \, dx\)

Hints

- In a), compare the numerator with the derivative of the denominator. - In b), compare one factor with the derivative of the exponent. - Change the limits when you substitute. - Recall the antiderivatives of \(\frac{1}{u}\) and \(e^u\).

Solution

1. For a), let \(u=x^3+1\), so \(du=3x^2\,dx\). The limits become \(u=2\) and \(u=9\). Therefore, \(\int_1^2\frac{3x^2}{x^3+1}\,dx=\int_2^9\frac{1}{u}\,du=\ln(9)-\ln(2)=\ln\left(\frac{9}{2}\right)\). 2. For b), let \(u=x^2-x\), so \(du=(2x-1)\,dx\). The limits become \(u=0\) and \(u=2\). Thus, \(\int_0^2(2x-1)e^{x^2-x}\,dx=\int_0^2e^u\,du=e^2-1\).

Answer

a) \(\ln\left(\frac{9}{2}\right)\) b) \(e^2-1\)
Integration by substitution 15
Evaluate each definite integral using an appropriate integration rule. a) \(\int_{1}^{3}\frac{2x-5}{x^2-5x+10} \, dx\) b) \(\int_{0}^{1}\frac{1}{(2x+2)^3} \, dx\)

Hints

- In a), compare the numerator with the derivative of the denominator. - Rewrite the denominator in b) using a negative exponent. - Account for the inner derivative of the linear expression. - Check each antiderivative by differentiating.

Solution

1. For a), let \(u=x^2-5x+10\), so \(du=(2x-5)\,dx\). Then \([\ln|x^2-5x+10|]_1^3=\ln(4)-\ln(6)=\ln\left(\frac{2}{3}\right)\). 2. For b), rewrite the integrand as \((2x+2)^{-3}\). An antiderivative is \(-\frac{1}{4}(2x+2)^{-2}\). 3. Evaluate: \([-\frac{1}{4(2x+2)^2}]_0^1=-\frac{1}{64}+\frac{1}{16}=\frac{3}{64}\).

Answer

a) \(\ln\left(\frac{2}{3}\right)\) b) \(\frac{3}{64}\)
Integration by substitution 16
Evaluate each integral. a) \(\int_{0}^{\sqrt{\pi}}x\sin(x^2) \, dx\) b) \(\int_{0}^{1}\frac{e^x}{e^x+1} \, dx\)

Hints

- Look for a factor that is the derivative of an inner expression. - Update the limits when changing variables. - Recall the derivative of \(e^x\). - Identify a logarithmic antiderivative pattern in b).

Solution

1. For a), let \(u=x^2\), so \(du=2x\,dx\). The limits become \(0\) and \(\pi\): \(\int_0^{\sqrt{\pi}}x\sin(x^2)\,dx=\frac{1}{2}\int_0^\pi\sin(u)\,du\). 2. Evaluate: \(\frac{1}{2}[-\cos(u)]_0^\pi=1\). 3. For b), let \(u=e^x+1\), so \(du=e^x\,dx\). The limits become \(2\) and \(e+1\): \(\int_0^1\frac{e^x}{e^x+1}\,dx=\int_2^{e+1}\frac{1}{u}\,du\). 4. Evaluate: \(\ln(e+1)-\ln(2)=\ln\left(\frac{e+1}{2}\right)\).

Answer

a) \(1\) b) \(\ln\left(\frac{e+1}{2}\right)\)
Integration by substitution 17
Find one antiderivative \(F\) of \(f(x)=6\cos(3x-1)+2\sin\left(\frac{x}{2}\right)\).

Hints

- Reverse the derivative rules for sine and cosine. - Account for each linear inner derivative. - Differentiate your result to check it.

Solution

1. For the cosine term, reverse the chain rule: \(\int 6\cos(3x-1)\,dx=2\sin(3x-1)\). 2. For the sine term, \(\int 2\sin(\frac{x}{2})\,dx=-4\cos(\frac{x}{2})\). 3. Therefore, \(F(x)=2\sin(3x-1)-4\cos\left(\frac{x}{2}\right)\).

Answer

\(F(x)=2\sin(3x-1)-4\cos\left(\frac{x}{2}\right)\)
Integration by substitution 18
Let \(f(x)=\frac{10}{2x+7}+\frac{1}{\sqrt{4x+9}}\) for \(x>-2.25\). Find one antiderivative \(F\).

Hints

- Rewrite the reciprocal square root using a negative exponent. - A reciprocal linear function leads to a logarithm. - Account for each linear inner derivative. - Differentiate your result to verify it.

Solution

1. For the first term, \(\int\frac{10}{2x+7}\,dx=5\ln(2x+7)\). The logarithm's argument is positive on the stated domain. 2. Rewrite the second term as \((4x+9)^{-\frac{1}{2}}\). Then \(\int(4x+9)^{-\frac{1}{2}}\,dx=\frac{1}{2}\sqrt{4x+9}\). 3. Thus \(F(x)=5\ln(2x+7)+\frac{1}{2}\sqrt{4x+9}\).

Answer

\(F(x)=5\ln(2x+7)+\frac{1}{2}\sqrt{4x+9}\)
Integration by substitution 19
Let \(f(x)=\left(\frac{1}{2}x+2\right)^6\). Identify the linear inner function \(u(x)\) and the outer function \(v(u)\), then find one antiderivative \(F\).

Hints

- Identify the expression inside the power. - Reverse the chain rule for a linear inner function. - Differentiate your result to verify it.

Solution

1. The inner function is \(u(x)=\frac{1}{2}x+2\), and the outer function is \(v(u)=u^6\). 2. An antiderivative of \(u^6\) with respect to \(u\) is \(\frac{1}{7}u^7\). 3. Since \(u'(x)=\frac{1}{2}\), divide by \(\frac{1}{2}\): \(F(x)=\frac{2}{7}\left(\frac{1}{2}x+2\right)^7\).

Answer

Inner function: \(u(x)=\frac{1}{2}x+2\) Outer function: \(v(u)=u^6\) Antiderivative: \(F(x)=\frac{2}{7}\left(\frac{1}{2}x+2\right)^7\)
Integration by substitution 20
Let \(f(x)=\frac{1}{\sqrt{4-3x}}\) for \(x<\frac{4}{3}\). Identify the inner function \(u(x)\) and outer function \(v(u)\), then find one antiderivative \(F\).

Hints

- Rewrite the reciprocal square root as a power. - Identify the derivative of the expression under the radical. - Reverse the power and chain rules.

Solution

1. Rewrite \(f(x)=(4-3x)^{-\frac{1}{2}}\). 2. The inner function is \(u(x)=4-3x\), and the outer function is \(v(u)=u^{-\frac{1}{2}}\). 3. An antiderivative of \(u^{-\frac{1}{2}}\) is \(2u^{\frac{1}{2}}\). Since \(u'(x)=-3\), divide by \(-3\): \(F(x)=-\frac{2}{3}\sqrt{4-3x}\).

Answer

Inner function: \(u(x)=4-3x\) Outer function: \(v(u)=u^{-\frac{1}{2}}\) Antiderivative: \(F(x)=-\frac{2}{3}\sqrt{4-3x}\)
Integration by substitution 21
Find one antiderivative for each function. a) \(f(x)=\left(\frac{2}{5}x-2\right)^4\) b) \(g(x)=\frac{3}{(1-2x)^2}\) c) \(h(x)=2\cos\left(4x+\frac{\pi}{2}\right)\)

Hints

- Identify the linear inner function in each expression. - Divide by the derivative of the inner function when reversing the chain rule. - Rewrite the rational power in b) using a negative exponent. - Differentiate each result to check it.

Solution

1. For a), reverse the power and chain rules: \(F(x)=\frac{1}{2}\left(\frac{2}{5}x-2\right)^5\). 2. For b), rewrite the integrand as \(3(1-2x)^{-2}\). An antiderivative is \(G(x)=\frac{3}{2}(1-2x)^{-1}=\frac{3}{2(1-2x)}\). 3. For c), account for the inner derivative \(4\): \(H(x)=\frac{1}{2}\sin\left(4x+\frac{\pi}{2}\right)\).

Answer

a) \(F(x)=\frac{1}{2}\left(\frac{2}{5}x-2\right)^5\) b) \(G(x)=\frac{3}{2(1-2x)}\) c) \(H(x)=\frac{1}{2}\sin\left(4x+\frac{\pi}{2}\right)\)
Integration by substitution 22
Let \(f(x)=4e^{2x-1}\). Find one antiderivative \(F\), then use it to evaluate \(\int_{0.5}^{1}f(x) \, dx\).

Hints

- Account for the derivative of the linear exponent. - Use the Fundamental Theorem after finding the antiderivative. - Recall that \(e^0=1\).

Solution

1. Reverse the chain rule to obtain \(F(x)=2e^{2x-1}\). 2. Apply the Fundamental Theorem: \(\int_{0.5}^{1}f(x)\,dx=[2e^{2x-1}]_{0.5}^{1}\). 3. Evaluate: \(2e^1-2e^0=2e-2\).

Answer

One antiderivative is \(F(x)=2e^{2x-1}\), and the integral equals \(2e-2\).
Integration by substitution 23
Evaluate the definite integral using a linear substitution: \(\int_{0}^{3}\frac{4}{2x+2} \, dx\).

Hints

- Which expression controls where the denominator is zero? - What constant factor appears when that expression is differentiated? - What happens to the endpoint values after you switch variables?

Solution

1. Let \(u=2x+2\), so \(du=2\,dx\). The limits become \(u=2\) and \(u=8\). 2. Then \(\int_0^3\frac{4}{2x+2}\,dx=2\int_2^8\frac{1}{u}\,du\). 3. Evaluate: \(2[\ln|u|]_2^8=2\ln(4)=4\ln(2)\).

Answer

\(4\ln(2)\)
Integration by substitution 24
Evaluate the integral using a linear substitution: \(\int_{-1}^{2}\frac{6}{12-3x} \, dx\).

Hints

- Track the negative sign when transforming \(dx\). - Reversing the new limits can remove that negative sign. - Recall the logarithmic antiderivative. - Combine the logarithm difference into one logarithm.

Solution

1. Let \(u=12-3x\), so \(du=-3\,dx\). The limits become \(u=15\) and \(u=6\). 2. Then \(\int_{-1}^{2}\frac{6}{12-3x}\,dx=-2\int_{15}^{6}\frac{1}{u}\,du=2\int_6^{15}\frac{1}{u}\,du\). 3. Evaluate: \(2[\ln|u|]_6^{15}=2\ln\left(\frac{15}{6}\right)=2\ln\left(\frac{5}{2}\right)\).

Answer

\(2\ln\left(\frac{5}{2}\right)\)
Integration by substitution 25
Find one antiderivative \(F\) for each function. a) \(f(x)=-2e^{4-0.5x}\) b) \(f(x)=(6x-9)e^{x^2-3x+1}\)

Hints

- In a), account for the derivative of the linear exponent. - In b), compare the outside factor with the derivative of the exponent. - Think of the chain rule in reverse.

Solution

1. For a), reverse the chain rule. The derivative of \(4-0.5x\) is \(-0.5\), so \(F(x)=\frac{-2}{-0.5}e^{4-0.5x}=4e^{4-0.5x}\). 2. For b), the derivative of \(x^2-3x+1\) is \(2x-3\), and \(6x-9=3(2x-3)\). Therefore, \(F(x)=3e^{x^2-3x+1}\).

Answer

a) \(F(x)=4e^{4-0.5x}\) b) \(F(x)=3e^{x^2-3x+1}\)
Integration by substitution 26
For \(x\ne 0\), find one antiderivative \(F\) of \(f(x)=\frac{4x-6}{x^2-3x+10}+\frac{1}{x^2}\).

Hints

- Compare the numerator of the first fraction with the derivative of its denominator. - Use the logarithmic antiderivative pattern. - Rewrite the second term with a negative exponent.

Solution

1. The derivative of \(x^2-3x+10\) is \(2x-3\), and \(4x-6=2(2x-3)\). Thus, \(\int\frac{4x-6}{x^2-3x+10}\,dx=2\ln(x^2-3x+10)\). The quadratic is always positive because its discriminant is \(9-40=-31\). 2. Rewrite \(\frac{1}{x^2}\) as \(x^{-2}\): \(\int x^{-2}\,dx=-x^{-1}=-\frac{1}{x}\). 3. Therefore, \(F(x)=2\ln(x^2-3x+10)-\frac{1}{x}\).

Answer

\(F(x)=2\ln(x^2-3x+10)-\frac{1}{x}\)
Integration by substitution 27
Use substitution to evaluate exactly: \(\int_0^2\frac{3x}{x^2+1}\,\text{d}x\). Your answer must state the substitution, the transformed definite integral with new bounds, and the final value.

Hints

- Choose an inner expression whose derivative is present in the numerator up to a constant factor. - Change both bounds when you change the integration variable. - After substitution, the integrand should be a constant multiple of \(1/u\).

Solution

1. Let \(u=x^2+1\). Then \(\text{d}u=2x\,\text{d}x\), so \(3x\,\text{d}x=\frac{3}{2}\,\text{d}u\). 2. When \(x=0\), \(u=1\); when \(x=2\), \(u=5\). 3. Therefore \(\int_0^2\frac{3x}{x^2+1}\,\text{d}x=\frac{3}{2}\int_1^5\frac{1}{u}\,\text{d}u\). 4. Evaluating gives \(\frac{3}{2}[\ln u]_1^5=\frac{3}{2}\ln5\).

Answer

Use \(u=x^2+1\), so \(\text{d}u=2x\,\text{d}x\) and \(\int_0^2\frac{3x}{x^2+1}\,\text{d}x=\frac{3}{2}\int_1^5\frac{1}{u}\,\text{d}u=\frac{3}{2}\ln5\).
Integration by substitution 28
Find one antiderivative \(F\) of the integrand, then evaluate \(\int_0^1\frac{4x}{2x^2+1}\,dx\).

Hints

- Differentiate the denominator. - Look for the logarithmic antiderivative pattern. - Apply the bounds after finding an antiderivative.

Solution

1. The numerator is the derivative of the denominator, so \(F(x)=\ln(2x^2+1)\). 2. Apply the Fundamental Theorem: \(\int_0^1\frac{4x}{2x^2+1}\,dx=[\ln(2x^2+1)]_0^1\). 3. Evaluate: \(\ln(3)-\ln(1)=\ln(3)\).

Answer

One antiderivative is \(F(x)=\ln(2x^2+1)\). The integral equals \(\ln(3)\).
Integration by substitution 29
Evaluate \(\int_0^{\sqrt{e-1}}\frac{x}{x^2+1}\,dx\). Compare the numerator with the derivative of the denominator.

Hints

- Differentiate the denominator. - Adjust the constant factor to match the logarithmic pattern. - Simplify the expression at the upper bound before evaluating the logarithm. - Recall \(\ln(e)=1\) and \(\ln(1)=0\).

Solution

1. Since the derivative of \(x^2+1\) is \(2x\), an antiderivative is \(F(x)=\frac{1}{2}\ln(x^2+1)\). 2. Apply the bounds: \(\left[\frac{1}{2}\ln(x^2+1)\right]_0^{\sqrt{e-1}}\) \(=\frac{1}{2}\ln(e)-\frac{1}{2}\ln(1)=\frac{1}{2}\).

Answer

\(\frac{1}{2}\)
Integration by substitution 30
Evaluate \(\int_1^2 2x(x^2-1)^3\,dx\). Explain how the structure of the integrand helps you find an antiderivative.

Hints

- Compare the factor outside the power with the derivative of the expression inside it. - Think of the chain rule in reverse. - Differentiate your proposed antiderivative to check it. - Apply the bounds only after finding an antiderivative.

Solution

1. The integrand has the form \(g'(x)(g(x))^3\), where \(g(x)=x^2-1\) and \(g'(x)=2x\). 2. Reversing the chain rule gives the antiderivative \(G(x)=\frac{1}{4}(x^2-1)^4\). 3. Apply the Fundamental Theorem: \(\left[\frac{1}{4}(x^2-1)^4\right]_1^2=\frac{1}{4}(3^4)-0=\frac{81}{4}\).

Answer

\(\frac{81}{4}=20.25\)
Integration by substitution 31
Let \(h(x)=\ln(x^2+5)\). a) Find \(h'(x)\). b) Use the result from part a) to give one antiderivative \(K\) of \(k(x)=\frac{x}{x^2+5}\).

Hints

- Use the chain rule to differentiate the logarithm. - Compare the function in b) with your derivative from a). - Account for the constant factor when reversing differentiation.

Solution

1. By the chain rule, \(h'(x)=\frac{1}{x^2+5}\cdot 2x=\frac{2x}{x^2+5}\). 2. Since \(k(x)=\frac{1}{2}h'(x)\), one antiderivative is \(K(x)=\frac{1}{2}h(x)=\frac{1}{2}\ln(x^2+5)\).

Answer

a) \(h'(x)=\frac{2x}{x^2+5}\) b) \(K(x)=\frac{1}{2}\ln(x^2+5)\)
Integration by substitution 32
Evaluate exactly: \(\int_0^{\frac{\pi}{2}}\frac{\cos(x)}{\sin(x)+2}\,dx\).

Hints

- Compare the numerator with the derivative of the denominator. - Use the logarithmic antiderivative pattern. - Evaluate the sine values at the bounds. - Combine the difference of logarithms.

Solution

1. The numerator is the derivative of \(\sin(x)+2\), so an antiderivative is \(F(x)=\ln(\sin(x)+2)\). The logarithm argument is positive on the interval. 2. Apply the bounds: \([\ln(\sin(x)+2)]_0^{\frac{\pi}{2}}=\ln(3)-\ln(2)\). 3. Use the quotient property of logarithms: \(\ln(3)-\ln(2)=\ln\left(\frac{3}{2}\right)\).

Answer

\(\ln\left(\frac{3}{2}\right)\)
Integration by substitution 33
Find one antiderivative \(F\) of \(f(x)=x(2x^2-5)^4\).

Hints

- Differentiate the expression inside the power. - Rewrite the outside factor to match that derivative. - Apply the power rule after substituting.

Solution

1. Let \(u=2x^2-5\), so \(du=4x\,dx\) and \(x\,dx=\frac{1}{4}du\). 2. Then \(\int x(2x^2-5)^4\,dx=\frac{1}{4}\int u^4\,du\) \(=\frac{1}{20}u^5\). 3. Substitute back: \(F(x)=\frac{1}{20}(2x^2-5)^5\).

Answer

\(F(x)=\frac{1}{20}(2x^2-5)^5\)
Integration by substitution 34
Let \(f(x)=\frac{x^2}{x^3+8}\) on the domain \(x>-2\). Find one antiderivative \(F\).

Hints

- Differentiate the denominator. - Compare that derivative with the numerator. - Use the logarithmic antiderivative pattern. - Use the domain to determine whether absolute value is needed.

Solution

1. The derivative of \(x^3+8\) is \(3x^2\), so \(f(x)=\frac{1}{3}\cdot\frac{3x^2}{x^3+8}\). 2. Apply the logarithmic antiderivative pattern: \(F(x)=\frac{1}{3}\ln|x^3+8|\). 3. Since \(x>-2\), the expression \(x^3+8\) is positive. Therefore, \(F(x)=\frac{1}{3}\ln(x^3+8)\).

Answer

\(F(x)=\frac{1}{3}\ln(x^3+8)\)
Integration by substitution 35
Find one antiderivative \(F\) of the integrand, then evaluate \(\int_0^1(3x^2+1)(x^3+x+1)^2\,dx\).

Hints

- Compare the first factor with the derivative of the expression inside the power. - Reverse the chain rule or use substitution. - Apply the bounds after finding the antiderivative.

Solution

1. Let \(u=x^3+x+1\), so \(du=(3x^2+1)\,dx\). 2. Then \(\int(3x^2+1)(x^3+x+1)^2\,dx=\int u^2\,du=\frac{u^3}{3}\). Thus, \(F(x)=\frac{1}{3}(x^3+x+1)^3\). 3. Evaluate: \(F(1)-F(0)=\frac{1}{3}(3^3)-\frac{1}{3}(1^3)=\frac{26}{3}\).

Answer

One antiderivative is \(F(x)=\frac{1}{3}(x^3+x+1)^3\). The integral equals \(\frac{26}{3}\).
Integration by substitution 36
Let \(f(x)=\frac{e^x}{e^x+3}\). Find one antiderivative \(F\), then evaluate \(\int_0^{\ln(2)}f(x)\,dx\).

Hints

- Compare the numerator with the derivative of the denominator. - Use the logarithmic antiderivative pattern. - Recall that \(e^{\ln(a)}=a\). - Combine the difference of logarithms.

Solution

1. The numerator is the derivative of the denominator, so \(F(x)=\ln(e^x+3)\). 2. Apply the bounds: \([\ln(e^x+3)]_0^{\ln(2)}=\ln(5)-\ln(4)\). 3. Combine the logarithms: \(\ln(5)-\ln(4)=\ln\left(\frac{5}{4}\right)\).

Answer

One antiderivative is \(F(x)=\ln(e^x+3)\). The integral equals \(\ln\left(\frac{5}{4}\right)\).
Integration by substitution 37
For \(x\ge -1\), find one antiderivative \(F\) of \(f(x)=x^2\sqrt{x^3+1}\).

Hints

- Differentiate the expression under the square root. - Use that expression as the substitution. - Rewrite the square root as a fractional power. - Substitute the original variable back at the end.

Solution

1. Let \(u=x^3+1\), so \(du=3x^2\,dx\) and \(x^2\,dx=\frac{1}{3}du\). 2. Then \(\int x^2\sqrt{x^3+1}\,dx=\frac{1}{3}\int u^{1/2}\,du\) \(=\frac{1}{3}\cdot\frac{2}{3}u^{3/2}\). 3. Substitute back: \(F(x)=\frac{2}{9}(x^3+1)^{3/2}\).

Answer

\(F(x)=\frac{2}{9}(x^3+1)^{3/2}\)
Integration by substitution 38
Find one antiderivative of the integrand, then evaluate \(\int_0^1 12x^2(x^3+1)^3\,dx\).

Hints

- Compare the outside factor with the derivative of the expression inside the power. - Use substitution and transform the bounds. - Check the antiderivative by differentiating with the chain rule. - Evaluate the transformed power integral.

Solution

1. Let \(u=x^3+1\), so \(du=3x^2\,dx\) and \(12x^2\,dx=4\,du\). The new bounds are \(u=1\) and \(u=2\). 2. Then \(\int_0^1 12x^2(x^3+1)^3\,dx=4\int_1^2u^3\,du\). 3. An antiderivative of the original integrand is \(F(x)=(x^3+1)^4\). 4. Evaluate: \([u^4]_1^2=2^4-1^4=15\).

Answer

One antiderivative is \(F(x)=(x^3+1)^4\). The integral equals \(15\).
Integration by substitution 39
Find one antiderivative of \(f(x)=\frac{x}{\sqrt{x^2+9}}\), then use it to evaluate \(\int_0^4\frac{x}{\sqrt{x^2+9}}\,dx\).

Hints

- Compare the numerator with the derivative of the expression under the square root. - Rewrite the reciprocal square root as a negative power. - Either transform the bounds or substitute back before evaluating.

Solution

1. Let \(u=x^2+9\), so \(du=2x\,dx\). 2. Then \(\int\frac{x}{\sqrt{x^2+9}}\,dx=\frac{1}{2}\int u^{-1/2}\,du=\sqrt{u}\). Thus, \(F(x)=\sqrt{x^2+9}\). 3. Evaluate: \([\sqrt{x^2+9}]_0^4=5-3=2\).

Answer

One antiderivative is \(F(x)=\sqrt{x^2+9}\). The integral equals \(2\).
Integration by substitution 40
Evaluate exactly: \(\int_0^2\frac{x}{x^2+2}\,dx\).

Hints

- Differentiate the denominator. - Compare that derivative with the numerator. - Use the logarithmic antiderivative pattern. - Combine the logarithms at the end.

Solution

1. The derivative of \(x^2+2\) is \(2x\), so an antiderivative is \(F(x)=\frac{1}{2}\ln(x^2+2)\). 2. Evaluate: \(\left[\frac{1}{2}\ln(x^2+2)\right]_0^2=\frac{1}{2}(\ln(6)-\ln(2))\). 3. Combine the logarithms: \(\frac{1}{2}\ln\left(\frac{6}{2}\right)=\frac{1}{2}\ln(3)\).

Answer

\(\frac{1}{2}\ln(3)\)
Integration by substitution 41
Evaluate \(\int_0^1 2x(x^2+1)^2\,dx\) using \(u=x^2+1\). Change the limits to \(u\)-values and complete the calculation without returning to \(x\).

Hints

- The differential \(du\) replaces the complete factor \(2x\,dx\). - Substitute both original endpoints into the formula for \(u\). - After changing the limits, evaluate entirely in the new variable.

Solution

1. Let \(u=x^2+1\), so \(du=2x\,dx\). 2. When \(x=0\), \(u=1\). When \(x=1\), \(u=2\). 3. Therefore, \(\int_0^1 2x(x^2+1)^2\,dx=\int_1^2u^2\,du=\left[\frac{u^3}{3}\right]_1^2=\frac73\).

Answer

\(\frac73\)
Integration by substitution 42
The graph of \(f(x)=2x\) has a shaded region beneath it. Use \(u=x^2\) to rewrite the shaded area as a definite integral in \(u\), and find the area.
Figure for problem 562586

Hints

- Read the shaded interval from the graph. - Differentiate the given substitution and check the factor in the original integrand. - Rewrite each limit in terms of \(u\), then integrate the new expression.

Solution

1. The shaded area is \(\int_0^2 2x\,\text{d}x\), read from the graph. 2. With \(u=x^2\), \(\text{d}u=2x\,\text{d}x\). The bounds become \(u=0\) and \(u=4\). 3. The transformed integral is \(\int_0^4 1\,\text{d}u=4\).

Answer

\(\int_0^4 1\,\text{d}u=4\) square units
Integration by substitution 43
Use \(u=x^2+2x+5\) to find \(\int\frac{x+1}{\sqrt{x^2+2x+5}}\,\text{d}x\). Check your answer by differentiating it.

Hints

- Compare the numerator with the derivative of the expression inside the square root. - Once you switch to \(u\), rewrite the square root as a power before integrating. - Differentiate your result to check both the function and its constant factor.

Solution

1. With \(u=x^2+2x+5\), \(\text{d}u=2(x+1)\,\text{d}x\), so \((x+1)\,\text{d}x=\frac{1}{2}\,\text{d}u\). 2. The integral becomes \(\frac{1}{2}\int u^{-1/2}\,\text{d}u=\sqrt{u}+C=\sqrt{x^2+2x+5}+C\). 3. Differentiating gives \(\frac{2x+2}{2\sqrt{x^2+2x+5}}=\frac{x+1}{\sqrt{x^2+2x+5}}\), as required.

Answer

\(\sqrt{x^2+2x+5}+C\); its derivative is \(\frac{x+1}{\sqrt{x^2+2x+5}}\).
Integration by substitution 44
Find the antiderivative \(F\) of \(f(x)=2x\sqrt{x^2+9}\) whose graph passes through \(P(0, 20)\).

Hints

- Compare the factor outside the square root with the derivative of the expression inside it. - A substitution can simplify an integrand when one factor is the derivative of another expression. - Use the given point to determine the constant of integration. - Rewrite the square root as a power with exponent \(\frac{1}{2}\).

Solution

1. Use the substitution \(u=x^2+9\), so \(du=2x\,dx\). 2. Then \(\int 2x\sqrt{x^2+9}\,dx=\int u^{\frac{1}{2}}\,du=\frac{2}{3}u^{\frac{3}{2}}+C\). 3. Substitute back: \(F(x)=\frac{2}{3}(x^2+9)^{\frac{3}{2}}+C\). 4. Use \(F(0)=20\): \(\frac{2}{3}(9)^{\frac{3}{2}}+C=20\). Since \(9^{\frac{3}{2}}=27\), this gives \(18+C=20\), so \(C=2\). 5. Therefore, \(F(x)=\frac{2}{3}(x^2+9)^{\frac{3}{2}}+2\).

Answer

\(F(x)=\frac{2}{3}(x^2+9)^{\frac{3}{2}}+2\)
Integration by substitution 45
For each function \(f\), a proposed antiderivative \(F\) is shown. Check each proposal. Describe any error and give a correct antiderivative. For d), require a formula valid on every interval in the full domain of \(f\). a) \(f(x)=\sin(3x)\); proposed \(F(x)=-3\cos(3x)\) b) \(f(x)=e^{2x-4}\); proposed \(F(x)=0.5e^{2x-4}\) c) \(f(x)=(4x+2)^3\); proposed \(F(x)=\frac{1}{4}(4x+2)^4\) d) \(f(x)=\frac{1}{0.5x+1}\); proposed \(F(x)=2\ln(0.5x+1)\)

Hints

- Differentiate each proposed antiderivative. - For a linear inner function, compare multiplication by the inner derivative with division by it. - Consider why the antiderivative of \(\frac{g'(x)}{g(x)}\) is written with \(\ln|g(x)|\).

Solution

1. For A, differentiate the proposal: \(\frac{d}{dx}[-3\cos(3x)]=9\sin(3x)\), not \(\sin(3x)\). The inner derivative should be divided out. A correct antiderivative is \(F(x)=-\frac{1}{3}\cos(3x)\). 2. For B, \(\frac{d}{dx}[0.5e^{2x-4}]=0.5\cdot 2e^{2x-4}=e^{2x-4}\), so the proposal is correct. 3. For C, \(\frac{d}{dx}[\frac{1}{4}(4x+2)^4]=4(4x+2)^3\). The proposal does not divide by the inner derivative \(4\). A correct antiderivative is \(F(x)=\frac{1}{16}(4x+2)^4\). 4. For D, differentiating \(2\ln|0.5x+1|\) gives \(2\cdot\frac{0.5}{0.5x+1}=\frac{1}{0.5x+1}\). The absolute value makes the formula valid on intervals on either side of \(x=-2\). Thus a correct full-domain formula is \(F(x)=2\ln|0.5x+1|\).

Answer

a) Incorrect; the inner derivative was multiplied instead of divided. A correct antiderivative is \(F(x)=-\frac{1}{3}\cos(3x)\). b) Correct. c) Incorrect; the factor from the inner derivative was not divided out. A correct antiderivative is \(F(x)=\frac{1}{16}(4x+2)^4\). d) The proposed formula is not valid on intervals where \(0.5x+1<0\). A full-domain formula is \(F(x)=2\ln|0.5x+1|\).
Integration by substitution 46
Each function \(f\) is paired with a proposed antiderivative \(F\). Identify the incorrect proposals, explain each error, and correct it. a) \(f(x)=\frac{x}{x^2+1}\); proposed \(F(x)=\ln(x^2+1)\) b) \(f(x)=3x^2e^{x^3}\); proposed \(F(x)=e^{x^3}\) c) \(f(x)=\frac{e^x}{e^x+2}\); proposed \(F(x)=e^x\ln(e^x+2)\) d) \(f(x)=2\cos(x)\sin(x)\); proposed \(F(x)=\sin^2(x)\)

Hints

- Differentiate each proposed antiderivative using the chain and product rules. - Look for the structure \(\frac{g'(x)}{g(x)}\). - Check whether a constant factor is needed to match the derivative exactly.

Solution

1. For A, \(\frac{d}{dx}\ln(x^2+1)=\frac{2x}{x^2+1}\), which is twice the given function. A correct antiderivative is \(F(x)=\frac{1}{2}\ln(x^2+1)\). 2. For B, \(\frac{d}{dx}e^{x^3}=3x^2e^{x^3}\), so the proposal is correct. 3. For C, the numerator is the derivative of the denominator. Therefore, \(\int\frac{e^x}{e^x+2}\,dx=\ln(e^x+2)+C\). The proposed product differentiates to additional terms, so it is incorrect. 4. For D, \(\frac{d}{dx}\sin^2(x)=2\sin(x)\cos(x)\), so the proposal is correct.

Answer

a) Incorrect; a factor of \(\frac{1}{2}\) is needed. A correct antiderivative is \(F(x)=\frac{1}{2}\ln(x^2+1)\). b) Correct. c) Incorrect; the numerator is already the derivative of the denominator. A correct antiderivative is \(F(x)=\ln(e^x+2)\). d) Correct.
Integration by substitution 47
Find the exact value of the definite integral \(\int_{0}^{2}\left(\frac{2x}{x^2+1}+(3x-1)^2\right) \, dx\).

Hints

- Split the integrand into two simpler terms. - In the rational term, compare the numerator with the derivative of the denominator. - For \((3x-1)^2\), account for the derivative of the linear inner function. - Evaluate each part before adding the results.

Solution

1. Split the integral into two parts: \(\int_0^2\frac{2x}{x^2+1}\,dx+\int_0^2(3x-1)^2\,dx\). 2. For the first part, use \(u=x^2+1\), so \(du=2x\,dx\). Then \(\int_0^2\frac{2x}{x^2+1}\,dx=[\ln(x^2+1)]_0^2=\ln(5)\). 3. For the second part, an antiderivative is \(\frac{1}{9}(3x-1)^3\). Therefore, \([\frac{1}{9}(3x-1)^3]_0^2=\frac{1}{9}[5^3-(-1)^3]=14\). 4. Add the results to obtain \(14+\ln(5)\).

Answer

\(14+\ln(5)\)
Integration by substitution 48
Evaluate each definite integral. a) \(\int_{0}^{2}xe^{-\frac{1}{2}x^2} \, dx\) b) \(\int_{0}^{\pi}\left(\frac{1}{2}\sin(x)+\cos\left(\frac{x}{2}\right)\right) \, dx\)

Hints

- In a), compare the derivative of the exponent with the factor outside the exponential. - Integrate the two terms in b) separately. - When integrating \(\cos(kx)\), account for the constant \(k\). - Substitute the limits carefully and check signs of trigonometric values.

Solution

1. For a), let \(u=-\frac{1}{2}x^2\), so \(du=-x\,dx\). Then an antiderivative is \(-e^{-\frac{1}{2}x^2}\). 2. Evaluate: \([-e^{-\frac{1}{2}x^2}]_0^2=-e^{-2}+1=1-e^{-2}\). 3. For b), integrate term by term. An antiderivative is \(-\frac{1}{2}\cos(x)+2\sin\left(\frac{x}{2}\right)\). 4. Evaluate: \([ -\frac{1}{2}\cos(x)+2\sin(\frac{x}{2}) ]_0^\pi=(\frac{1}{2}+2)-(-\frac{1}{2})=3\).

Answer

a) \(1-e^{-2}\) b) \(3\)
Integration by substitution 49
Find an antiderivative \(F\) of \(f(t)=4(1-2t)^3\) that satisfies \(F(1)=5\).

Hints

- How do you integrate a power of a linear expression? - Differentiate your antiderivative to check the chain-rule factor. - Substitute the given input and output to determine the constant.

Solution

1. Use substitution for the linear expression: \(F(t)=-\frac{1}{2}(1-2t)^4+C\). 2. Apply the condition \(F(1)=5\): \(-\frac{1}{2}(1-2)^4+C=5\). 3. Since \((1-2)^4=1\), \(-\frac{1}{2}+C=5\), so \(C=\frac{11}{2}\). 4. Thus, \(F(t)=-\frac{1}{2}(1-2t)^4+\frac{11}{2}\).

Answer

\(F(t)=-\frac{1}{2}(1-2t)^4+\frac{11}{2}\)
Integration by substitution 50
For each integral, decide whether it can be evaluated using only the power, sum, and constant multiple rules; a linear substitution; or the logarithmic rule \(\int\frac{g'(x)}{g(x)}\,dx=\ln|g(x)|+C\). Evaluate every integral that can be handled by those methods. 1. \(\int_{1}^{2}\frac{x^2+1}{x^2} \, dx\) 2. \(\int_{0}^{1}\frac{3x^2}{x^3+1} \, dx\) 3. \(\int_{0}^{2}e^{0.5x} \, dx\) 4. \(\int_{1}^{2}\ln(x) \, dx\) 5. \(\int_{0}^{1}\frac{1}{x^2+1} \, dx\)

Hints

- Rewrite the rational expression in 1 as a sum of powers of \(x\). - In 2, compare the numerator with the derivative of the denominator. - In 3, account for the derivative of \(0.5x\). - For 4 and 5, ask whether any of the specifically listed antiderivative patterns applies.

Solution

1. For 1, use the power, sum, and constant multiple rules. Rewrite the integrand as \(1+x^{-2}\). Then \([x-\frac{1}{x}]_1^2=\frac{3}{2}\). 2. For 2, use the logarithmic rule with \(g(x)=x^3+1\), since \(g'(x)=3x^2\). Thus \([\ln(x^3+1)]_0^1=\ln(2)\). 3. For 3, use a linear substitution, or account directly for the inner derivative. An antiderivative is \(2e^{0.5x}\), so \([2e^{0.5x}]_0^2=2e-2\). 4. The fourth integral cannot be evaluated using only the listed methods; a standard method is integration by parts. 5. The fifth integral cannot be evaluated using only the listed methods; its antiderivative involves \(\arctan(x)\).

Answer

1. Power, sum, and constant multiple rules: \(\frac{3}{2}\) 2. Logarithmic rule: \(\ln(2)\) 3. Linear substitution: \(2e-2\) 4. Not evaluable using only the listed methods. 5. Not evaluable using only the listed methods.
Integration by substitution 51
For each integral, decide whether it can be evaluated using the power rule, possibly after expanding; a linear substitution; or the logarithmic rule. Evaluate every integral that can be handled by those methods. 1. \(\int_{0}^{2}(x-1)(x+1) \, dx\) 2. \(\int_{2}^{5}\frac{1}{2x-3} \, dx\) 3. \(\int_{0}^{\pi}x\cos(x) \, dx\) 4. \(\int_{1}^{2}\frac{2x+3}{x^2+3x} \, dx\) 5. \(\int_{0}^{1}\sqrt{x^2+1} \, dx\)

Hints

- Expand the product in 1 before integrating. - In 2, use the antiderivative pattern for the reciprocal of a linear function. - In 4, compare the numerator with the derivative of the denominator. - Decide whether the listed rules include a method for products such as \(x\cos(x)\).

Solution

1. For 1, use the power rule after expanding: \((x-1)(x+1)=x^2-1\). Then \([\frac{1}{3}x^3-x]_0^2=\frac{2}{3}\). 2. For 2, use a linear substitution, or the reciprocal-of-a-linear-function pattern. An antiderivative is \(\frac{1}{2}\ln|2x-3|\), so \([\frac{1}{2}\ln|2x-3|]_2^5=\frac{1}{2}\ln(7)\). 3. The third integral cannot be evaluated using only the listed methods; a standard method is integration by parts. 4. For 4, use the logarithmic rule because the numerator is the derivative of the denominator. Therefore, \([\ln(x^2+3x)]_1^2=\ln(10)-\ln(4)=\ln(\frac{5}{2})\). 5. The fifth integral cannot be evaluated using only the listed methods; it requires a more advanced substitution or a known special antiderivative.

Answer

1. Power rule after expanding: \(\frac{2}{3}\) 2. Linear substitution: \(\frac{1}{2}\ln(7)\) 3. Not evaluable using only the listed methods. 4. Logarithmic rule: \(\ln(\frac{5}{2})\) 5. Not evaluable using only the listed methods.
Integration by substitution 52
Let \(f(x)=\frac{6}{\sqrt{2x+9}}\). Find the antiderivative \(F\) whose graph passes through \((0,10)\).

Hints

- Rewrite the reciprocal square root using a negative exponent. - Use the integration rule for \((ax+b)^n\). - The point gives a specific value of the antiderivative. - Substitute the constant back into the final expression.

Solution

1. Rewrite the integrand as \(f(x)=6(2x+9)^{-\frac{1}{2}}\). 2. Integrate using substitution: \(F(x)=6\sqrt{2x+9}+C\). 3. Use \(F(0)=10\): \(6\sqrt{9}+C=10\). 4. Since \(18+C=10\), \(C=-8\). Therefore, \(F(x)=6\sqrt{2x+9}-8\).

Answer

\(F(x)=6\sqrt{2x+9}-8\)
Integration by substitution 53
Let \(f(x)=4-\sqrt{2x+4}\), with domain \([-2,\infty)\). Evaluate \(\int_{-2}^{0}f(x)\,dx\).

Hints

- Rewrite the square root as a rational power. - Use a substitution for the linear expression inside the radical. - Find an antiderivative before evaluating at the limits. - Be careful with the sign of the lower-limit value.

Solution

1. To integrate the radical term, let \(u=2x+4\), so \(du=2\,dx\) and \(dx=\frac{1}{2}\,du\). 2. Then \(\int\sqrt{2x+4}\,dx=\frac{1}{2}\int u^{1/2}\,du=\frac{1}{3}u^{3/2}+C\). Thus, an antiderivative of \(f\) is \(F(x)=4x-\frac{1}{3}(2x+4)^{3/2}\). 3. Evaluate: \(F(0)=-\frac{8}{3}\) and \(F(-2)=-8\). 4. Therefore, \(F(0)-F(-2)=-\frac{8}{3}+8=\frac{16}{3}\).

Answer

\(\frac{16}{3}\)
Integration by substitution 54
Let \(g(x)=\sqrt{4-\frac{1}{2}x}\) for \(x\leq8\). Find the exact value of \(\int_{0}^{8}g(x)\,dx\).

Hints

- Rewrite the radical as a rational power. - Use a substitution for the linear expression inside the radical. - Account for the coefficient of \(x\) in the substitution. - Simplify the expression inside the radical at each limit before evaluating the power.

Solution

1. Let \(u=4-\frac{1}{2}x\). Then \(du=-\frac{1}{2}\,dx\), so \(dx=-2\,du\). 2. An antiderivative is \(-2\int u^{1/2}\,du=-\frac{4}{3}u^{3/2}+C\). Therefore, \(G(x)=-\frac{4}{3}\left(4-\frac{1}{2}x\right)^{3/2}\). 3. Evaluate: \(G(8)=0\) and \(G(0)=-\frac{4}{3}\cdot4^{3/2}=-\frac{32}{3}\). 4. Thus, \(G(8)-G(0)=\frac{32}{3}\).

Answer

\(\frac{32}{3}\)
Integration by substitution 55
Complete the denominator in \(\int_{0}^{1}\frac{e^x}{\square} \, dx\) as directed. a) Choose a denominator so the integrand simplifies by cancellation to a basic integral. Evaluate it. b) Choose a denominator so the logarithmic integration rule applies. Evaluate that integral.

Hints

- What happens when the numerator and denominator are identical? - For the logarithmic rule, how must the numerator relate to the denominator? - Which functions have derivative \(e^x\)?

Solution

1. For a), choose the denominator \(e^x\). Then the integrand is \(1\), so \(\int_0^1 1\,dx=1\). 2. For b), choose \(e^x+1\). Its derivative is the numerator \(e^x\), so \(\int_0^1\frac{e^x}{e^x+1}\,dx=[\ln(e^x+1)]_0^1\). 3. Evaluate to obtain \(\ln(e+1)-\ln(2)=\ln\left(\frac{e+1}{2}\right)\).

Answer

a) Denominator \(e^x\); value \(1\) b) One possible denominator is \(e^x+1\); value \(\ln\left(\frac{e+1}{2}\right)\)
Integration by substitution 56
Let \(f(x)=\frac{4x}{2x^2+3}+\sin(2x+1)\). Find a formula for \(f'(x)\) and one antiderivative \(F(x)\).

Hints

- Work with the two terms separately. - Use the quotient rule for the rational term when differentiating. - Compare the rational numerator with the derivative of its denominator when integrating. - Apply the chain rule and its reverse to the trigonometric term.

Solution

1. Differentiate the rational term using the quotient rule: \(\frac{d}{dx}\left(\frac{4x}{2x^2+3}\right)=\frac{4(2x^2+3)-4x(4x)}{(2x^2+3)^2}=\frac{12-8x^2}{(2x^2+3)^2}\). 2. Differentiate the sine term using the chain rule: \(\frac{d}{dx}\sin(2x+1)=2\cos(2x+1)\). Thus \(f'(x)=\frac{12-8x^2}{(2x^2+3)^2}+2\cos(2x+1)\). 3. For an antiderivative, the numerator \(4x\) is the derivative of \(2x^2+3\), so the first term integrates to \(\ln(2x^2+3)\). 4. The sine term integrates to \(-\frac{1}{2}\cos(2x+1)\). Therefore, \(F(x)=\ln(2x^2+3)-\frac{1}{2}\cos(2x+1)\).

Answer

\(f'(x)=\frac{12-8x^2}{(2x^2+3)^2}+2\cos(2x+1)\) \(F(x)=\ln(2x^2+3)-\frac{1}{2}\cos(2x+1)\)
Integration by substitution 57
Let \(f(x)=\frac{1}{\sqrt{2x+9}}\) for \(x>-\frac{9}{2}\). Find the antiderivative \(F\) satisfying \(F(0)=5\).

Hints

- Rewrite the reciprocal square root as a negative power. - First find the general antiderivative with \(C\). - Use \(F(0)=5\) to determine \(C\). - Differentiate your result to verify it.

Solution

1. Rewrite \(f(x)=(2x+9)^{-\frac{1}{2}}\). 2. Reverse the power and chain rules: \(F(x)=\sqrt{2x+9}+C\). 3. Use the condition \(F(0)=5\): \(3+C=5\), so \(C=2\). 4. Therefore, \(F(x)=\sqrt{2x+9}+2\).

Answer

\(F(x)=\sqrt{2x+9}+2\)
Integration by substitution 58
Evaluate \(\int_0^2\left(\frac{1}{2}x+1\right)^3 \, dx\) in two ways and compare the results. 1. Expand the integrand completely and integrate term by term. 2. Use a linear substitution.

Hints

- Use the binomial theorem or repeated multiplication to expand. - For substitution, identify the derivative of the linear inner function. - Update the limits after changing variables. - Compare the exact values from both approaches.

Solution

1. Expand: \(\left(\frac{1}{2}x+1\right)^3=\frac{1}{8}x^3+\frac{3}{4}x^2+\frac{3}{2}x+1\). 2. Integrate term by term: \([\frac{1}{32}x^4+\frac{1}{4}x^3+\frac{3}{4}x^2+x]_0^2=\frac{15}{2}\). 3. For substitution, let \(u=\frac{1}{2}x+1\), so \(du=\frac{1}{2}\,dx\). The limits become \(1\) and \(2\): \(2\int_1^2u^3\,du=2[\frac{1}{4}u^4]_1^2=\frac{15}{2}\). 4. Both methods give the same value.

Answer

\(\frac{15}{2}\) by both methods
Integration by substitution 59
Evaluate \(\int_0^1(1-2x)^4 \, dx\) in two ways. a) Expand the integrand and integrate term by term. b) Use a linear substitution. Compare the results.

Hints

- Use the binomial coefficients for a fourth power. - Track the negative derivative of \(1-2x\). - Update the limits after substitution. - Compare the exact results from both methods.

Solution

1. Expand: \((1-2x)^4=1-8x+24x^2-32x^3+16x^4\). 2. Integrate term by term: \([x-4x^2+8x^3-8x^4+\frac{16}{5}x^5]_0^1=\frac{1}{5}\). 3. For substitution, let \(u=1-2x\), so \(du=-2\,dx\). The limits become \(1\) and \(-1\): \(-\frac{1}{2}\int_1^{-1}u^4\,du=\frac{1}{2}\int_{-1}^{1}u^4\,du=\frac{1}{5}\). 4. Both methods give the same value.

Answer

a) \(\frac{1}{5}\) b) \(\frac{1}{5}\). Both methods give the same result.
Integration by substitution 60
Evaluate the definite integral \(\int_{0}^{1}\left[(2x+1)^3-\frac{3}{(3x+1)^2}\right] \, dx\).

Hints

- Split the integral using linearity. - Reverse the power and chain rules for each linear inner function. - Rewrite the reciprocal square using a negative exponent. - Preserve the subtraction between the two terms.

Solution

1. An antiderivative of \((2x+1)^3\) is \(\frac{1}{8}(2x+1)^4\). Its contribution is \([\frac{1}{8}(2x+1)^4]_0^1=10\). 2. An antiderivative of \(\frac{3}{(3x+1)^2}\) is \(-\frac{1}{3x+1}\). Its contribution is \([-\frac{1}{3x+1}]_0^1=\frac{3}{4}\). 3. The second term is subtracted in the original integrand, so the total is \(10-\frac{3}{4}=\frac{37}{4}\).

Answer

\(\frac{37}{4}\)
Integration by substitution 61
Evaluate \(\int_{0}^{4}\left[\sin\left(\frac{\pi x}{4}\right)+\frac{1}{\sqrt{2x+1}}\right] \, dx\).

Hints

- Treat the two terms separately. - Account for the inner derivative in the sine term. - Rewrite the reciprocal square root as a negative power. - Use the cosine values at \(0\) and \(\pi\).

Solution

1. An antiderivative of \(\sin(\frac{\pi x}{4})\) is \(-\frac{4}{\pi}\cos(\frac{\pi x}{4})\). Its contribution is \([ -\frac{4}{\pi}\cos(\frac{\pi x}{4}) ]_0^4=\frac{8}{\pi}\). 2. Rewrite the second term as \((2x+1)^{-\frac{1}{2}}\). An antiderivative is \(\sqrt{2x+1}\), so its contribution is \([\sqrt{2x+1}]_0^4=3-1=2\). 3. Add the results to obtain \(\frac{8}{\pi}+2\).

Answer

\(\frac{8}{\pi}+2\)
Integration by substitution 62
Evaluate the definite integral \(\int_{0}^{1}(4x^2-4x+1)^3 \, dx\).

Hints

- Factor the quadratic as a perfect square. - Simplify the power of a power. - Reverse the power and chain rules. - Track the sign at the lower limit.

Solution

1. Recognize the perfect square: \(4x^2-4x+1=(2x-1)^2\). 2. Therefore, the integrand is \((2x-1)^6\). 3. An antiderivative is \(\frac{1}{14}(2x-1)^7\). 4. Evaluate: \([\frac{1}{14}(2x-1)^7]_0^1=\frac{1}{14}-(-\frac{1}{14})=\frac{1}{7}\).

Answer

\(\frac{1}{7}\)
Integration by substitution 63
Find one antiderivative \(F\) for each function. a) \(f(x)=(e^{2x}+1)^2\) b) \(f(x)=\frac{4e^{2x}}{e^{2x}+3}\)

Hints

- Expand the square in a) before integrating. - In b), compare the numerator with the derivative of the denominator. - Recall the logarithmic antiderivative pattern.

Solution

1. For a), first expand: \((e^{2x}+1)^2=e^{4x}+2e^{2x}+1\). Integrate term by term: \(F(x)=\frac{1}{4}e^{4x}+e^{2x}+x\). 2. For b), let \(u=e^{2x}+3\). Then \(du=2e^{2x}\,dx\), so \(\int\frac{4e^{2x}}{e^{2x}+3}\,dx=2\int\frac{1}{u}\,du=2\ln|u|\). Since \(e^{2x}+3>0\), \(F(x)=2\ln(e^{2x}+3)\).

Answer

a) \(F(x)=\frac{1}{4}e^{4x}+e^{2x}+x\) b) \(F(x)=2\ln(e^{2x}+3)\)
Integration by substitution 64
For \(x\ne -2\), find one antiderivative \(F\) of \(f(x)=\frac{x+3}{x+2}-\frac{e^x}{2e^x+4}\).

Hints

- Rewrite the first fraction as a constant plus a simpler fraction. - Compare the numerator of the second fraction with the derivative of its denominator. - Adjust the constant factor before using the logarithmic pattern.

Solution

1. Rewrite the first fraction: \(\frac{x+3}{x+2}=\frac{x+2+1}{x+2}=1+\frac{1}{x+2}\). Therefore, \(\int\frac{x+3}{x+2}\,dx=x+\ln|x+2|\). 2. For the second fraction, the derivative of \(2e^x+4\) is \(2e^x\). Hence, \(\int\frac{e^x}{2e^x+4}\,dx=\frac{1}{2}\ln(2e^x+4)\). 3. Combine the results: \(F(x)=x+\ln|x+2|-\frac{1}{2}\ln(2e^x+4)\).

Answer

\(F(x)=x+\ln|x+2|-\frac{1}{2}\ln(2e^x+4)\)
Integration by substitution 65
Find one antiderivative \(F\) for each function. a) \(f(x)=8(2x+7)^3\) b) \(f(x)=(3x^2-6)(x^3-6x+1)^5\) c) \(f(x)=\frac{2x+5}{x^2+5x-2}\) d) \(f(x)=x(x+1)^4\)

Hints

- Look for an inner function and its derivative. - For a product, check whether one factor is the derivative of the expression inside a power. - For a fraction, compare the numerator with the derivative of the denominator. - In d), rewrite \(x\) in terms of \(x+1\).

Solution

1. For a), reverse the chain rule: \(F(x)=(2x+7)^4\). 2. For b), the first factor is the derivative of \(x^3-6x+1\), so \(F(x)=\frac{1}{6}(x^3-6x+1)^6\). 3. For c), the numerator is the derivative of the denominator, so \(F(x)=\ln|x^2+5x-2|\). 4. For d), write \(x=(x+1)-1\): \(x(x+1)^4=(x+1)^5-(x+1)^4\). Therefore, \(F(x)=\frac{1}{6}(x+1)^6-\frac{1}{5}(x+1)^5\).

Answer

a) \(F(x)=(2x+7)^4\) b) \(F(x)=\frac{1}{6}(x^3-6x+1)^6\) c) \(F(x)=\ln|x^2+5x-2|\) d) \(F(x)=\frac{1}{6}(x+1)^6-\frac{1}{5}(x+1)^5\)
Integration by substitution 66
Find one antiderivative \(F\) for each function. a) \(f(x)=-6e^{3-2x}\) b) \(f(x)=(x+2)e^{x^2+4x}\) c) \(f(x)=5\sin(5x-\pi)\) d) \(f(x)=\frac{6x}{(x^2+4)^2}\)

Hints

- Account for the derivative of each exponent. - Reverse the sine and cosine derivative rules carefully. - Rewrite the fraction in d) with a negative power. - Differentiate each result to check it.

Solution

1. For a), account for the derivative \(-2\) of the exponent: \(F(x)=3e^{3-2x}\). 2. For b), the derivative of \(x^2+4x\) is \(2(x+2)\), so \(F(x)=\frac{1}{2}e^{x^2+4x}\). 3. For c), reverse the chain rule: \(F(x)=-\cos(5x-\pi)\). 4. For d), use \(u=x^2+4\), so \(du=2x\,dx\): \(\int\frac{6x}{(x^2+4)^2}\,dx=3\int u^{-2}\,du=-3u^{-1}\). Thus, \(F(x)=-\frac{3}{x^2+4}\).

Answer

a) \(F(x)=3e^{3-2x}\) b) \(F(x)=\frac{1}{2}e^{x^2+4x}\) c) \(F(x)=-\cos(5x-\pi)\) d) \(F(x)=-\frac{3}{x^2+4}\)
Integration by substitution 67
The graph shows a water-flow rate \(p(t)=\frac{4t}{t^2+1}\) in liters per minute, with \(t\) in minutes. How much water enters during the shaded time interval? Use substitution and give an exact answer.
Figure for problem 562611

Hints

- Read both times from the shaded part of the graph. - Look for a part of the denominator whose derivative is related to the numerator. - Remember that a change of variable also changes the limits of a definite integral.

Solution

1. Read the shaded interval from the graph: \(1\le t\le2\). The added volume is \(\int_1^2\frac{4t}{t^2+1}\,\text{d}t\). 2. Let \(u=t^2+1\), so \(\text{d}u=2t\,\text{d}t\). The bounds become \(u=2\) and \(u=5\). 3. The volume is \(2\int_2^5\frac{1}{u}\,\text{d}u=2\ln\left(\frac{5}{2}\right)\) liters.

Answer

\(2\ln\left(\frac{5}{2}\right)\,\text{L}\)
Integration by substitution 68
Let \(f(x)=xe^{-x^2}+\sqrt{3x-2}\) for \(x\ge\frac{2}{3}\). Find a formula for \(f'(x)\) and one antiderivative \(F(x)\).

Hints

- Use the product and chain rules on the exponential term when differentiating. - Rewrite the square root as a power. - For integration, compare \(x\) with the derivative of \(-x^2\). - Reverse the power and chain rules for the linear expression under the square root.

Solution

1. For \(x>\frac{2}{3}\), differentiate the first term using the product and chain rules: \(\frac{d}{dx}[xe^{-x^2}]=e^{-x^2}-2x^2e^{-x^2}=(1-2x^2)e^{-x^2}\). 2. Differentiate the square-root term: \(\frac{d}{dx}(3x-2)^{\frac{1}{2}}=\frac{3}{2\sqrt{3x-2}}\). Thus \(f'(x)=(1-2x^2)e^{-x^2}+\frac{3}{2\sqrt{3x-2}}\) for \(x>\frac{2}{3}\). 3. For an antiderivative of the first term, use \(u=-x^2\), giving \(-\frac{1}{2}e^{-x^2}\). 4. For the second term, reverse the power and chain rules: \(\int(3x-2)^{\frac{1}{2}}\,dx=\frac{2}{9}(3x-2)^{\frac{3}{2}}\). 5. Therefore, \(F(x)=-\frac{1}{2}e^{-x^2}+\frac{2}{9}(3x-2)^{\frac{3}{2}}\).

Answer

\(f'(x)=(1-2x^2)e^{-x^2}+\frac{3}{2\sqrt{3x-2}}\) for \(x>\frac{2}{3}\) \(F(x)=-\frac{1}{2}e^{-x^2}+\frac{2}{9}(3x-2)^{\frac{3}{2}}\) for \(x\ge\frac{2}{3}\)

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