Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Definite Integration

Question:

$∫\frac{dx}{x(x^n+1)}$ is equal to

Options:

$\frac{1}{n}log_e(\frac{x^n}{x^n+1})+c$

$-\frac{1}{n}log_e(\frac{x^n+1}{x^n})+c$

$log_e(\frac{x^n}{x^n+1})+c$

none of these 

Correct Answer:

$-\frac{1}{n}log_e(\frac{x^n+1}{x^n})+c$

Explanation:

Let $I=∫\frac{dx}{x(x^n+1)}=∫\frac{dx}{x^{n+1}(1+\frac{1}{x^n})}$.

If $(1+\frac{1}{x^n})=p$, then $-\frac{n}{x^{n+1}}dx=dp$

$⇒I=-\frac{1}{n}∫\frac{dp}{p}=\frac{-1}{n}log_ep+c=-\frac{1}{n}log_e(\frac{x^n+1}{x^n})+c$

Hence (B) is the correct answer.