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

  • question_answer
    The solution of the differential equation \[\frac{dy}{dx}=1+x+y+xy\] is    [AISSE 1985; AI CBSE 1990; MP PET 2003]

    A)                 \[\log (1+y)=x+\frac{{{x}^{2}}}{2}+c\]     

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

    C)                 \[\log (1+y)=\log (1+x)+c\]               

    D)                 None of these

    Correct Answer: A

    Solution :

                       \[\frac{dy}{dx}=1+x+y+xy\]         Þ \[\frac{dy}{dx}=(1+x)(1+y)\] Þ \[\frac{dy}{dx}+\sin \left( \frac{x+y}{2} \right)=\sin \left( \frac{x-y}{2} \right)\]                                 On integrating, we get \[\log (1+y)=\frac{{{x}^{2}}}{2}+x+c\].


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