Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Indefinite Integration

Question:

$\int \frac{f(x) g'(x)-g(x) f'(x)}{f(x) . g(x)}\{\log g(x)-\log f(x)\} d x$ is equal to

Options:

$\log _e\left\{\frac{g(x)}{f(x)}\right\}+C$

$\frac{1}{2}\left\{\log _e \frac{g(x)}{f(x)}\right\}^2+C$

$\frac{g(x)}{f(x)} \log _e \frac{g(x)}{f(x)}+C$

none of these

Correct Answer:

$\frac{1}{2}\left\{\log _e \frac{g(x)}{f(x)}\right\}^2+C$

Explanation:

Let

$I=\int \frac{f(x) g'(x)-g(x) f'(x)}{f(x) . g(x)}\{\log g(x)-\log f(x)\} d x$

$\Rightarrow I=\int \log \left\{\frac{g(x)}{f(x)}\right\} . d\left\{\log \frac{g(x)}{f(x)}\right\}=\frac{1}{2}\left\{\log _e \frac{g(x)}{f(x)}\right\}^2+C$