Indefinite Integrals — Question 4

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Question 4

Evaluate the integral ∫(xlnx+1x)dx.\int \left( \sqrt{x}\,\ln x + \frac{1}{\sqrt{x}} \right)\,dx.

Original worksheet page 1: question and worked solution for 5-1-004
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Question 4 - Solution

We first rewrite the integrand using exponents: xln⁡x+1x=x1/2ln⁡x+x−1/2.\sqrt{x}\,\ln x + \frac{1}{\sqrt{x}} = x^{1/2}\ln x + x^{-1/2}.

For the first term, apply integration by parts with u=ln⁡x,dv=x1/2dx.u=\ln x, \qquad dv=x^{1/2}\,dx. Then du=1xdx,v=23x3/2.du=\frac{1}{x}\,dx, \qquad v=\frac{2}{3}x^{3/2}. Thus, ∫x1/2ln⁡xdx=23x3/2ln⁡x−23∫x1/2dx=23x3/2ln⁡x−49x3/2.\int x^{1/2}\ln x\,dx = \frac{2}{3}x^{3/2}\ln x - \frac{2}{3}\int x^{1/2}\,dx = \frac{2}{3}x^{3/2}\ln x - \frac{4}{9}x^{3/2}.

For the second term, ∫x−1/2dx=2x1/2.\int x^{-1/2}\,dx = 2x^{1/2}.

Combining results: 23x3/2ln⁡x−49x3/2+2x1/2+C\boxed{ \frac{2}{3}x^{3/2}\ln x - \frac{4}{9}x^{3/2} + 2x^{1/2} + C }

Original worksheet page 2: question and worked solution for 5-1-004

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