Differential Equations Question 128

Question: The solution of differential equation $ \frac{dy}{dx}+y=1 $ is

[Pb. CET 2000]

Options:

A) $ y=1+c{e^{-x}} $

B) $ y=1-c{e^{-x}} $

C) $ y=x+c{e^{-x}} $

D) $ y=x-c{e^{-x}} $

Show Answer

Answer:

Correct Answer: A

Solution:

$ \frac{dy}{dx}+y=1 $ ; I.F. $ ={e^{\int{Pdx}}}={e^{\int{dx}}}=e^{x} $

Hence solution is $ y.e^{x}=\int{e^{x}dx+c} $

$ ye^{x}=e^{x}+c $

Therefore $ y=1+c{e^{-x}} $ .