Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Differential Equations

Question:

The integrating factor of the differential equation, $x^2\frac{dy}{dx}+xy = \log_ex$ is equal to

Options:

$e^x$

$e^{\frac{x^2}{2}}$

$x$

$\log_ex$

Correct Answer:

$x$

Explanation:

The correct answer is Option (3) → $x$

The given equation is

$x^{2}\frac{dy}{dx}+xy=\log x$

Divide by $x^{2}$:

$\frac{dy}{dx}+\frac{1}{x}y=\frac{\log x}{x^{2}}$

This is linear of the form

$\frac{dy}{dx}+P(x)y=Q(x)$ where $P(x)=\frac{1}{x}$

Integrating factor is

$IF=e^{\int \frac{1}{x}dx}$

$=e^{\log x}$

$=x$

Integrating factor is $x$.