Integration by parts Worked Solutions — A-Level Maths

Fully worked, step-by-step solutions to A-Level Integration by parts questions. See exactly how to solve problems on integration by parts, LIATE, integrate ln x, loop integral.

integration by partsLIATEintegrate ln xloop integralarea under curve
A-Level70 questionsStep-by-step solutions
Question 1
2 markseasy
Find xexdx\int x e^{x}\,dx.

Worked solution

  1. Choose uu and dvdx\dfrac{dv}{dx} using LIATE

    u=x,dvdx=exu=x,\qquad \frac{dv}{dx}=e^{x}

    Let uu be the factor that simplifies when differentiated; integrate the rest.

  2. Substitute into the formula

    xexdx=xexexdx\int x e^{x}\,dx=x e^{x}-\int e^{x}\,dx

    Replace uvuv and vdudxdx\int v\,\dfrac{du}{dx}\,dx using the pieces above.

  3. State the final answer

    xexdx=(x1)ex+c\int x e^{x}\,dx=\left(x - 1\right) e^{x}+c

    Combine the terms and include the constant of integration.

Answer
(x1)ex+c\left(x - 1\right) e^{x}+c
Question 2
2 markseasy
Find xe2xdx\int x e^{2 x}\,dx.

Worked solution

  1. Choose uu and dvdx\dfrac{dv}{dx} using LIATE

    u=x,dvdx=e2xu=x,\qquad \frac{dv}{dx}=e^{2 x}

    Let uu be the factor that simplifies when differentiated; integrate the rest.

  2. Substitute into the formula

    xe2xdx=xe2x2e2x2dx\int x e^{2 x}\,dx=\frac{x e^{2 x}}{2}-\int \frac{e^{2 x}}{2}\,dx

    Replace uvuv and vdudxdx\int v\,\dfrac{du}{dx}\,dx using the pieces above.

  3. State the final answer

    xe2xdx=(2x1)e2x4+c\int x e^{2 x}\,dx=\frac{\left(2 x - 1\right) e^{2 x}}{4}+c

    Combine the terms and include the constant of integration.

Answer
(2x1)e2x4+c\frac{\left(2 x - 1\right) e^{2 x}}{4}+c
Question 3
2 markseasy
Find xsin(x)dx\int x \sin{\left(x \right)}\,dx.

Worked solution

  1. Choose uu and dvdx\dfrac{dv}{dx} using LIATE

    u=x,dvdx=sin(x)u=x,\qquad \frac{dv}{dx}=\sin{\left(x \right)}

    Let uu be the factor that simplifies when differentiated; integrate the rest.

  2. Substitute into the formula

    xsin(x)dx=xcos(x)cos(x)dx\int x \sin{\left(x \right)}\,dx=- x \cos{\left(x \right)}-\int - \cos{\left(x \right)}\,dx

    Replace uvuv and vdudxdx\int v\,\dfrac{du}{dx}\,dx using the pieces above.

  3. State the final answer

    xsin(x)dx=xcos(x)+sin(x)+c\int x \sin{\left(x \right)}\,dx=- x \cos{\left(x \right)} + \sin{\left(x \right)}+c

    Combine the terms and include the constant of integration.

Answer
xcos(x)+sin(x)+c- x \cos{\left(x \right)} + \sin{\left(x \right)}+c
Question 4
2 markseasy
Find xcos(x)dx\int x \cos{\left(x \right)}\,dx.

Worked solution

  1. Choose uu and dvdx\dfrac{dv}{dx} using LIATE

    u=x,dvdx=cos(x)u=x,\qquad \frac{dv}{dx}=\cos{\left(x \right)}

    Let uu be the factor that simplifies when differentiated; integrate the rest.

  2. Substitute into the formula

    xcos(x)dx=xsin(x)sin(x)dx\int x \cos{\left(x \right)}\,dx=x \sin{\left(x \right)}-\int \sin{\left(x \right)}\,dx

    Replace uvuv and vdudxdx\int v\,\dfrac{du}{dx}\,dx using the pieces above.

  3. State the final answer

    xcos(x)dx=xsin(x)+cos(x)+c\int x \cos{\left(x \right)}\,dx=x \sin{\left(x \right)} + \cos{\left(x \right)}+c

    Combine the terms and include the constant of integration.

Answer
xsin(x)+cos(x)+cx \sin{\left(x \right)} + \cos{\left(x \right)}+c
Question 5
2 markseasy
Find xsin(2x)dx\int x \sin{\left(2 x \right)}\,dx.

Worked solution

  1. Choose uu and dvdx\dfrac{dv}{dx} using LIATE

    u=x,dvdx=sin(2x)u=x,\qquad \frac{dv}{dx}=\sin{\left(2 x \right)}

    Let uu be the factor that simplifies when differentiated; integrate the rest.

  2. Substitute into the formula

    xsin(2x)dx=xcos(2x)2cos(2x)2dx\int x \sin{\left(2 x \right)}\,dx=- \frac{x \cos{\left(2 x \right)}}{2}-\int - \frac{\cos{\left(2 x \right)}}{2}\,dx

    Replace uvuv and vdudxdx\int v\,\dfrac{du}{dx}\,dx using the pieces above.

  3. State the final answer

    xsin(2x)dx=xcos(2x)2+sin(2x)4+c\int x \sin{\left(2 x \right)}\,dx=- \frac{x \cos{\left(2 x \right)}}{2} + \frac{\sin{\left(2 x \right)}}{4}+c

    Combine the terms and include the constant of integration.

Answer
xcos(2x)2+sin(2x)4+c- \frac{x \cos{\left(2 x \right)}}{2} + \frac{\sin{\left(2 x \right)}}{4}+c

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