J & K CET Engineering J and K - CET Engineering Solved Paper-2011

  • question_answer
    The general solution of the differential equation \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{e}^{2x}}+{{e}^{-x}}\] is

    A)  \[4{{e}^{2x}}+{{e}^{-x}}+{{C}_{1}}x+{{C}_{2}}\]

    B)  \[\frac{1}{4}{{e}^{2x}}-{{e}^{-x}}+C\]

    C)  \[\frac{1}{4}{{e}^{2x}}+{{e}^{-x}}+{{C}_{1}}x+{{C}_{2}}\]

    D)  \[\frac{1}{4}{{e}^{2x}}-{{e}^{-x}}+{{C}_{1}}x+{{C}_{2}}\]

    Correct Answer: C

    Solution :

    \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{e}^{2x}}+{{e}^{-x}}\] ?..(i) Integrating on both sides w.r.t.x, \[\int{\frac{d}{dx}\left( \frac{dy}{dx} \right)}\,dx=\int{({{e}^{2x}}+{{e}^{-x}})dx}\] \[\Rightarrow \] \[\frac{dy}{dx}=\frac{{{e}^{2x}}}{2}-{{e}^{-x}}+{{C}_{1}}\] Again integration on both sides w.r.t.x, \[\Rightarrow \] \[\int{\frac{d}{dx}\,(y)\,dx=\int{\left( \frac{{{e}^{2x}}}{2}-{{e}^{-x}}+{{C}_{1}} \right)}}dx\] \[\Rightarrow \] \[y=\frac{{{e}^{2x}}}{4}+{{e}^{-x}}+{{C}_{1}}x+{{C}_{2}}\]


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