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

  • question_answer
    If \[\frac{dy}{dx}=\frac{xy+y}{xy+x}\], then the solution of the differential equation is           [SCRA 1980]

    A)                 \[y=x{{e}^{x}}+c\]          

    B)                 \[y={{e}^{x}}+c\]

    C)                 \[y=Ax{{e}^{x-y}}\]         

    D)                 \[y=x+A\]

    Correct Answer: C

    Solution :

                       \[\frac{dy}{dx}=\frac{xy+y}{xy+x}\] Þ \[\left( \frac{1+y}{y} \right)dy=\left( \frac{1+x}{x} \right)dx\]         On integrating both sides, we get         \[\log y+y=\log x+x+\log A\]                 Þ \[\log \left( \frac{y}{Ax} \right)=x-y\]Þ\[y=Ax{{e}^{x-y}}\]. 


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