JEE Main & Advanced Mathematics Differential Equations Question Bank Linear defferential equations

  • question_answer
    An integrating factor of the differential equation \[x\frac{dy}{dx}+y\log x=x{{e}^{x}}{{x}^{-\frac{1}{2}\log x}}\], \[(x>0)\] is [Kerala (Engg.) 2005]

    A)                 \[{{x}^{\log x}}\]               

    B)                 \[{{(\sqrt{x})}^{\log x}}\]

    C)                 \[{{(\sqrt{e})}^{\log x}}\] 

    D)                 \[{{e}^{{{x}^{2}}}}\]

    E)                 \[{{x}^{2}}/2\]

    Correct Answer: B

    Solution :

                       \[\frac{dy}{dx}+\left( \frac{\log x}{x} \right)y={{e}^{x}}{{x}^{-\frac{1}{2}\log x}}\] I.F.\[={{e}^{\int{\frac{\log x}{x}dx}}}={{e}^{\frac{1}{2}{{(\log x)}^{2}}}}={{\left( {{e}^{\frac{1}{2}(\log x)}} \right)}^{\log x}}\] \[={{\left( {{e}^{\log \sqrt{x}}} \right)}^{\log x}}={{(\sqrt{x})}^{\log x}}\]


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