1.

\( \frac{d^{2} y}{d x^{2}}+\frac{d y}{d x}=\frac{1}{1+e^{x}} \)

Answer»

Given differential equation is

\(\frac{d^2y}{dx^2}+\frac{dy}{dx}=\frac{1}{1+e^x}\)\(=\frac{e^{-x}}{e^{-x}(1+e^x)}=\frac{e^{-x}}{e^{-x}+1}\) 

⇒ \(\int\frac{d^2y}{dx^2}dx+\int\frac{dy}{dx}dx\) = \(\int\frac{e^{-x}}{e^{-x}+1}dx\)(By taking integration w.r.t. x)

⇒ \(\frac{dy}{dx}+y = -log(e^{-x}+1)\) 

which is solution of given differential equation.



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