JEE Main & Advanced Mathematics Differential Equations Question Bank Linear defferential equations

  • question_answer
    The solution of the differential equation \[x\frac{dy}{dx}+y={{x}^{2}}+3x+2\] is

    A)                 \[xy=\frac{{{x}^{3}}}{3}+\frac{3}{2}{{x}^{2}}+2x+c\]     

    B)                 \[xy=\frac{{{x}^{4}}}{4}+{{x}^{3}}+{{x}^{2}}+c\]

    C)                 \[xy=\frac{{{x}^{4}}}{4}+\frac{{{x}^{3}}}{3}+{{x}^{2}}+c\]        

    D)                 \[xy=\frac{{{x}^{4}}}{4}+{{x}^{3}}+{{x}^{2}}+cx\]

    Correct Answer: A

    Solution :

                       \[x\frac{dy}{dx}+y={{x}^{2}}+3x+2\] Þ \[\frac{dy}{dx}+\frac{y}{x}=x+3+\frac{2}{x}\]         Here\[P=\frac{1}{x},\ Q=x+3+\frac{2}{x}\], therefore I.F. \[\frac{dy}{dx}=-1\]                 Now solve it.


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