JEE Main & Advanced Mathematics Differential Equations Question Bank Miscellaneous differential equations

  • question_answer
    The solution of  \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{\sec }^{2}}x+x{{e}^{x}}\]is        [DSSE 1985]

    A)                    \[y=\log (\sec x)+(x-2){{e}^{x}}+{{c}_{1}}x+{{c}_{2}}\]

    B)                    \[y=\log (\sec x)+(x+2){{e}^{x}}+{{c}_{1}}x+{{c}_{2}}\]

    C)            \[y=\log (\sec x)-(x+2){{e}^{x}}+{{c}_{1}}x+{{c}_{2}}\]

    D)            None of these

    Correct Answer: A

    Solution :

                       \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{\sec }^{2}}x+x{{e}^{x}}\]            On integrating, \[\frac{dy}{dx}=\tan x+x{{e}^{x}}-{{e}^{x}}+{{c}_{1}}\]            Again, \[y=\log (\sec x)+x{{e}^{x}}-{{e}^{x}}-{{e}^{x}}+{{c}_{1}}x+{{c}_{2}}\]                    Thus required solution is                    \[y=\log (\sec x)+(x-2){{e}^{x}}+{{c}_{1}}x+{{c}_{2}}\].


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