JEE Main & Advanced Mathematics Differential Equations Question Bank Variable Separable type differential equations

  • question_answer
    The solution of the differential equation \[(x-{{y}^{2}}x)dx=(y-{{x}^{2}}y)dy\] is              [DSSE 1984]

    A)                 \[(1-{{y}^{2}})={{c}^{2}}(1-{{x}^{2}})\]              

    B)                 \[(1+{{y}^{2}})={{c}^{2}}(1-{{x}^{2}})\]

    C)                 \[(1+{{y}^{2}})={{c}^{2}}(1+{{x}^{2}})\]          

    D)                 None of these

    Correct Answer: A

    Solution :

                       Given equation can be written as \[\frac{x}{1-{{x}^{2}}}dx=\frac{y}{1-{{y}^{2}}}dy\]                    On integrating we get \[-\frac{1}{2}\log (1-{{x}^{2}})=-\frac{1}{2}\log (1-{{y}^{2}})+\log c\]                    Þ \[\log (1-{{x}^{2}})-\log (1-{{y}^{2}})=-2\log c\] Þ \[\frac{1-{{x}^{2}}}{1-{{y}^{2}}}={{c}^{-2}}\]                                 Hence \[(1-{{y}^{2}})={{c}^{2}}(1-{{x}^{2}})\].


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