Differential Equations — Class 12 Maths Solution

exemplar objective MCQ NCERT EXEMP.Q.74,Page.201
Question

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

  • (a) $y = {e^{x - y}} - {x^2}{e^{ - y}} + C$
  • (b) ${e^y} - {e^x} = \frac{{{x^3}}}{3} + C$ ✓ Correct
  • (c) ${e^x} + {e^y} = \frac{{{x^3}}}{3} + C$
  • (d) ${e^x} - {e^y} = \frac{{{x^3}}}{3} + C$
Step-by-step Solution
Correct answer: option (b)

Given that,

$\frac{{dy}}{{dx}} = {e^{x - y}} + {x^2}{e^{ - y}}$

$\Rightarrow$ $\frac{{dy}}{{dx}} = {e^x}{e^{ - y}} + {x^2}{e^{ - y}}$

$\Rightarrow$ $\frac{{dy}}{{dx}} = \frac{{{e^x} + {x^2}}}{{{e^y}}}$

$\Rightarrow$ ${e^y}dy = \left( {{e^x} + {x^2}} \right)dx$

On integrating both sides,

we get
$\int {{e^y}} dy = \int {\left( {{e^x} + {x^2}} \right)} dx$

$\Rightarrow$ ${e^y} = {e^x} + \frac{{{x^3}}}{3} + C$

$\Rightarrow$ ${e^y} - {e^x} = \frac{{{x^3}}}{3} + C$

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