12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-6

  • question_answer
    The solution of the differential equation,\[{{\left( \mathbf{1}+\mathbf{x} \right)}^{\mathbf{2}}}\frac{dy}{dx}+{{\mathbf{y}}^{\mathbf{2}}}+\mathbf{1}=0\]is

    A)  \[ta{{n}^{-1}}x+ta{{n}^{-1}}y=ta{{n}^{-1}}c\]                 

    B)  \[ta{{n}^{-1}}x-ta{{n}^{-1}}y=ta{{n}^{-1}}c\]

    C)  \[-ta{{n}^{-1}}x+ta{{n}^{-1}}y=ta{{n}^{-1}}c\]

    D)  None of these

    Correct Answer: A

    Solution :

    [a] \[\because (1+{{x}^{2}})\frac{dy}{dx}+(1+{{y}^{2}})=0\] \[\Rightarrow (1+{{x}^{2}})dy=-(1+{{y}^{2}})dx\] \[\Rightarrow \frac{dy}{1+{{y}^{2}}}=-\frac{dx}{1+{{x}^{2}}}\]     Integrating/we have \[\int{\frac{dy}{1+{{y}^{2}}}=\int{-\frac{dx}{1+{{x}^{2}}}}}\] \[\Rightarrow ta{{n}^{-1}}y=-ta{{n}^{-1}}x+{{\tan }^{-1}}c\] Hence, option [a] is correct.


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