The differential equation $y\frac{{dy}}{{dx}} + x = C$ represents
- (a) family of hyperbolas
- (b) family of parabolas
- (c) family of ellipses
- (d) family of circles ✓ Correct
The differential equation $y\frac{{dy}}{{dx}} + x = C$ represents
Given that, $y\frac{{dy}}{{dx}} + x = C$
$\Rightarrow$ $y\frac{{dy}}{{dx}} = C - x$
$\Rightarrow$ $ydy = (C - x)dx$
On integrating both sides,
we get
$\frac{{{y^2}}}{2} = Cx - \frac{{{x^2}}}{2} + K$
$\Rightarrow$ $\frac{{{x^2}}}{2} + \frac{{{y^2}}}{2} = Cx + K$
$\Rightarrow$ $\frac{{{x^2}}}{2} + \frac{{{y^2}}}{2} - Cx = K$
which represent family of circles.
NCERT & Exemplar solution for CBSE Class 12 Mathematics, Differential Equations. Curated by Sachin Sharma. Free for all students.