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

  • question_answer
    Integrating factor of equation \[({{x}^{2}}+1)\frac{dy}{dx}+2xy={{x}^{2}}-1\] is [UPSEAT 2002]

    A)                 \[{{x}^{2}}+1\]

    B)                 \[\frac{2x}{{{x}^{2}}+1}\]

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

    D)                 None of these

    Correct Answer: A

    Solution :

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


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