CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The  differential   equation\[y\frac{dy}{dx}+x=c\]represents:

    A)  a family of hyperbolas

    B)  a family of circles whose centres are on the y-axis

    C)  a family of parabolas

    D)  a family of ellipse

    E)  a family of circles whose centres are on the x-axis

    Correct Answer: E

    Solution :

    We have, \[y\frac{dy}{dx}+x=c\] On it can be rewritten as                 \[ydy=(c-x)dx\] On integrating both sides, we get                 \[\int{y\,\,dy}=\int{(c-x)}\,dx\]                 \[\frac{{{y}^{2}}}{2}=cx-\frac{{{x}^{2}}}{2}+{{c}_{1}}\]                 \[\Rightarrow \,\,{{x}^{2}}+{{y}^{2}}\,-2cx={{c}_{1}}\] Which represents a family of circles whose centre is (c, 0) i. e., on the\[x-\]axis.


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