Differential Equations — Class 12 Maths Solution

exemplar objective MCQ NCERT EXEMP.Q.63,Page.199
Question

The general Solution of differential equation $\frac{{dy}}{{dx}} = {e^{\frac{{{x^2}}}{2}}} + xy$ is

  • (a) $y = C{e^{ - {x^2}/2}}$
  • (b) $y = C{{\rm{e}}^{{x^2}/2}}$
  • (c) $y = (x + C){e^{{x^2}/2}}$ ✓ Correct
  • (d) $y = (C - x){e^{{x^2}/2}}$
Step-by-step Solution
Correct answer: option (c)

Given that, $\frac{{dy}}{{dx}} = {e^{{x^2}/2}} + xy$

$\Rightarrow$ $\frac{{dy}}{{dx}} - xy = {e^{{x^2}/2}}$

Here, $P = - x,Q = {e^{{x^2}/2}}$

$\therefore$ $IF = {e^{\int - xdx}} = {e^{ - {x^2}/2}}$

The general Solution is
$y \cdot {e^{ - {x^2}/2}} = \int {{e^{ - {x^2}/2}}} - {e^{{x^2}/2}}dx + C$

$\Rightarrow$ $y{e^{ - {x^2}/2}} = \int 1 dx + C$

$\Rightarrow$ $y \cdot {e^{ - {x^2}/2}} = x + C$

$\Rightarrow$ $y = x{e^{{x^2}/2}} + C{e^{ + {x^2}/2}}$

$\Rightarrow$ $y = (x + C){e^{{x^2}/2}}$

NCERT & Exemplar solution for CBSE Class 12 Mathematics, Differential Equations. Curated by Sachin Sharma. Free for all students.