Consider the differential equation $\frac{dy}{dx}=\frac{y+1}{x+1}$, and y = 0 where x = 2. The value of y at x = 3 is:
Answer & explanation
Correct answer: option 2
The correct answer is option (2) → $\frac{1}{3}$
$\frac{dy}{dx}=\frac{y+1}{x+1}$
$⇒\int\frac{dy}{y+1}=\int\frac{dx}{x+1}$
$⇒ln|y+1|=ln|x+1|+C$
and,
$y=0$ when $x=2$
$∴ln|1|=ln|3|+C$
$⇒C=-ln|3|$
$∴ln|y+1|=ln|4|-ln|3|$
$ln|y+1|=ln|\frac{4}{3}|$
$⇒y+1=\frac{4}{3}$
$⇒3y=1$
$⇒y=\frac{1}{3}$