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

  • question_answer
    The solution of the differential equation\[{{x}^{2}}dy=-2xydx\] is [SCRA 1990]

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

    B)                 \[{{x}^{2}}{{y}^{2}}=c\]

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

    D)                 \[xy=c\]

    Correct Answer: C

    Solution :

                       \[{{x}^{2}}dy=-2xydx\] Þ \[\frac{1}{y}dy=-\frac{2x}{{{x}^{2}}}dx\]         On integrating, \[\log y=-2\log x+\log c\]                 Þ \[\log y=\log {{x}^{-2}}+\log c\]Þ \[\log y{{x}^{2}}=\log c\]or \[y{{x}^{2}}=c\].


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