The solution of the differentiable equation $2x\frac{dy}{dx}+y=14x^3, x>0$, is
Answer & explanation
Correct answer: option 3
$2x\frac{dy}{dx}+y=14x^3$ dividing by leading 2x
$⇒\frac{dy}{dx}\underbrace{\frac{1}{2x}}_{p}y=\underbrace{7x^2}_{q}$
Intergrating factor = $e^{\int pdx}=e^{\int\frac{1}{2x}dx}$
$=e^{\frac{1}{2}ln\,x}=e^{ln\sqrt{x}}=\sqrt{x}$
multiplying eqn with integrating factor
$\sqrt{x}\frac{dy}{dx}+\frac{1}{2\sqrt{x}}y=7x^{5/2}$
integrating both side w.r.t. x
$\int\sqrt{x}\frac{dy}{dx}+\frac{1}{2\sqrt{x}}ydx=7\int x^{5/2}dx$
$=\sqrt{x}y=7\frac{x^{7/2}}{7}×2+c$
$y=2x^3+cx^{-\frac{1}{2}}$