Integration by substitution Worked Solutions — A-Level Maths

Fully worked, step-by-step solutions to A-Level Integration by substitution questions. See exactly how to solve problems on substitution, reverse chain rule, exponential, logarithmic.

substitutionreverse chain ruleexponentiallogarithmicsurdtrigonometric
A-Level70 questionsStep-by-step solutions
Question 1
2 markseasy
Find 2x(x2+1)5dx\int 2 x \left(x^{2} + 1\right)^{5}\,dx.

Worked solution

  1. Choose the substitution and differentiate

    u=x2+1,du=2xdxu=x^{2} + 1,\quad du=2 x\,dx

    The derivative of the inner function is a factor of the integrand.

  2. Rewrite in terms of u and integrate

    u5du=u66+c\int u^{5}\,du=\frac{u^{6}}{6}+c

    Integrate the standard expression in u.

  3. State the final answer

    2x(x2+1)5dx=(x2+1)66+c\int 2 x \left(x^{2} + 1\right)^{5}\,dx=\frac{\left(x^{2} + 1\right)^{6}}{6}+c

    Remember to include the constant of integration.

Answer
(x2+1)66+c\frac{\left(x^{2} + 1\right)^{6}}{6}+c
Question 2
2 markseasy
Find 2xex2dx\int 2 x e^{x^{2}}\,dx.

Worked solution

  1. Choose the substitution and differentiate

    u=x2,du=2xdxu=x^{2},\quad du=2 x\,dx

    The derivative of the inner function is a factor of the integrand.

  2. Rewrite in terms of u and integrate

    eudu=eu+c\int e^{u}\,du=e^{u}+c

    Integrate the standard expression in u.

  3. State the final answer

    2xex2dx=ex2+c\int 2 x e^{x^{2}}\,dx=e^{x^{2}}+c

    Remember to include the constant of integration.

Answer
ex2+ce^{x^{2}}+c
Question 3
2 markseasy
Find xex2dx\int x e^{x^{2}}\,dx.

Worked solution

  1. Choose the substitution and differentiate

    u=x2,du=2xdxu=x^{2},\quad du=2 x\,dx

    The derivative of the inner function is a factor of the integrand.

  2. Rewrite in terms of u and integrate

    eu2du=eu2+c\int \frac{e^{u}}{2}\,du=\frac{e^{u}}{2}+c

    Integrate the standard expression in u.

  3. State the final answer

    xex2dx=ex22+c\int x e^{x^{2}}\,dx=\frac{e^{x^{2}}}{2}+c

    Remember to include the constant of integration.

Answer
ex22+c\frac{e^{x^{2}}}{2}+c
Question 4
2 markseasy
Find xx2+1dx\int \frac{x}{x^{2} + 1}\,dx.

Worked solution

  1. Choose the substitution and differentiate

    u=x2+1,du=2xdxu=x^{2} + 1,\quad du=2 x\,dx

    The derivative of the inner function is a factor of the integrand.

  2. Rewrite in terms of u and integrate

    12udu=ln(u)2+c\int \frac{1}{2 u}\,du=\frac{\ln{\left(u \right)}}{2}+c

    Integrate the standard expression in u.

  3. State the final answer

    xx2+1dx=ln(x2+1)2+c\int \frac{x}{x^{2} + 1}\,dx=\frac{\ln{\left(x^{2} + 1 \right)}}{2}+c

    Remember to include the constant of integration.

Answer
ln(x2+1)2+c\frac{\ln{\left(x^{2} + 1 \right)}}{2}+c
Question 5
2 markseasy
Find 3x2x3+1dx\int \frac{3 x^{2}}{x^{3} + 1}\,dx.

Worked solution

  1. Choose the substitution and differentiate

    u=x3+1,du=3x2dxu=x^{3} + 1,\quad du=3 x^{2}\,dx

    The derivative of the inner function is a factor of the integrand.

  2. Rewrite in terms of u and integrate

    1udu=ln(u)+c\int \frac{1}{u}\,du=\ln{\left(u \right)}+c

    Integrate the standard expression in u.

  3. State the final answer

    3x2x3+1dx=ln(x3+1)+c\int \frac{3 x^{2}}{x^{3} + 1}\,dx=\ln{\left(x^{3} + 1 \right)}+c

    Remember to include the constant of integration.

Answer
ln(x3+1)+c\ln{\left(x^{3} + 1 \right)}+c

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