JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    Solve\[(xy-1)\frac{dy}{dx}+{{y}^{2}}=0\]

    A) \[xy+\log x=C\]

    B) \[xy+\log y=C\]

    C) \[xy-\log y=C\] 

    D) \[xy-\log x=C\]

    Correct Answer: C

    Solution :

    Given, equation can be written as                 \[xy\,\,dy+{{y}^{2}}dx-dy=0\] On multiplying by\[\frac{1}{y}\], we get                 \[x\,\,dy+y\,\,dx-\frac{1}{y}dy=0\] \[\Rightarrow \]               \[d(xy)-\frac{1}{y}dy=0\] On integrating, we get \[\Rightarrow \]               \[\int{d}(xy)-\int{\frac{dy}{y}}=0\] \[\Rightarrow \]               \[xy-\log y=C\]


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