12th Class Mathematics Sample Paper Mathematics Sample Paper-2

  • question_answer
    Find the integrating factor of the differential equation \[\frac{dy}{dx}+y=\frac{1+y}{x}.\]

    Answer:

    We have,  \[\frac{dy}{dx}+y=\frac{1+y}{x}\] \[\Rightarrow \]   \[\frac{dy}{dx}+y=\frac{1}{x}+\frac{y}{x}\] \[\Rightarrow \]   \[\frac{dy}{dx}+y-\frac{y}{x}=\frac{1}{x}\] \[\Rightarrow \]\[\frac{dy}{dx}+y\left( 1-\frac{1}{x} \right)=\frac{1}{x}\] \[\Rightarrow \] \[\frac{dy}{dx}+y\left( \frac{x-1}{x} \right)=\frac{1}{x}\] Which is a linear differential equation of the form \[\frac{dy}{dx}+Py=Q,\] where \[P=\frac{x-1}{x}\] and \[Q=\frac{1}{x}\] Now, \[IF={{e}^{\int{Pdx}}}={{e}^{\int{\frac{x-1}{x}dx}}}={{e}^{\int{\left[ 1\,-\,\frac{1}{x} \right]}\,dx}}\]             \[={{e}^{x\,-\,\log \,x}}={{e}^{x}}\cdot {{e}^{-\log \,x}}\]             \[={{e}^{x}}\cdot {{e}^{\log \,{{x}^{-1}}}}={{e}^{x}}\cdot {{x}^{-1}}={{e}^{x}}.\frac{1}{x}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner