Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section A

Chapter

Differential Equations

Question:

Solution of the differential equation (x + xy)dy – y(1 – x2)dx = 0 is

Options:

$y=\log \frac{x}{y}-\frac{x^2}{2}+C$

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

$y=\log x y-\frac{x^2}{2}+C$

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

Correct Answer:

$y=\log \frac{x}{y}-\frac{x^2}{2}+C$

Explanation:

$(x+x y) d y-y\left(1-x^2\right) d x=0$

$\Rightarrow(x+x y) d y=y\left(1-x^2\right) d x$

so $\int \frac{1+y}{y} d y=\int \frac{1-x^2}{x} d x$

$\Rightarrow \int 1+\frac{1}{y} d y=\int \frac{1}{x}-x d x \Rightarrow y+\log y=\log x-\frac{x^2}{2}+C$

$\Rightarrow y=\log \frac{x}{y}-\frac{x^2}{2}+C$

Option: 1