JEE Main & Advanced JEE Main Paper (Held On 26 May 2012)

  • question_answer
    The integrating factor of the differential equation \[\left( {{x}^{2}}-1 \right)\frac{dy}{dx}+2xy=x\] is.   JEE Main Online Paper (Held On 26-May-2012)  

    A) \[\frac{1}{{{x}^{2}}-1}\]                

    B)                        \[{{x}^{2}}-1\]

    C)                        \[\frac{{{x}^{2}}-1}{x}\]                

    D)                        \[\frac{x}{{{x}^{2}}-1}\]

    Correct Answer: B

    Solution :

                    Given   differential   equation   is \[\left( {{x}^{2}}-1 \right)\frac{dy}{dx}+2xy=x\]\[\Rightarrow \]\[\frac{dy}{dx}+\frac{2x}{{{x}^{2}}-1}.y=\frac{x}{{{x}^{2}}-1}\] This is in linear form. Integrating factor \[\int\limits_{e}^{{}}{\frac{2x}{{{x}^{2}}-1}}dx=\int\limits_{e}^{{}}{\frac{dt}{t}}\]where\[t={{x}^{2}}-1\]\[={{e}^{\log t}}={{x}^{2}}-1\] Hence, required integrating factor \[={{x}^{2}}-1.\]


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