Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Indefinite Integration

Question:

$\int \frac{d x}{(2 x+1)(1+\sqrt{(2 x+1)}}$ is equal to :

Options:

$\tan ^{-1} \frac{\sqrt{2 x+1}}{1+\sqrt{2 x+1}}+c$

$\log _{e} \frac{\sqrt{2 x+1}}{1+\sqrt{2 x+1}}+c$

$\log _{e}\left(\frac{1+\sqrt{2 x+1}}{\sqrt{2 x+1}}\right)+c$

$\tan ^{-1} \frac{1+\sqrt{2 x+1}}{\sqrt{2 x+1}}+c$

Correct Answer:

$\log _{e} \frac{\sqrt{2 x+1}}{1+\sqrt{2 x+1}}+c$

Explanation:

$I=\int \frac{d x}{(2 x+1)(1+\sqrt{(2 x+1)}}$

so let $y=\sqrt{2x+1}$

$dy=\frac{1}{\sqrt{2x+1}}dx$

$⇒I=\int\frac{dy}{y(1+y)}=\int\frac{1}{y}-\frac{1}{1+y}dy$

$=\log y-\log 1+y+C$

$=\log\frac{y}{1+y}+C=\log\frac{\sqrt{2x+1}}{1+\sqrt{2x+1}}+C$