Manipal Engineering Manipal Engineering Solved Paper-2011

  • question_answer
    The equation of the circle which passes through the points (2, 3) and (4, 5) and the centre lies on the straight line\[y-4x+3=0\], is

    A) \[{{x}^{2}}+{{y}^{2}}+4x-10y+25=0\]

    B) \[{{x}^{2}}+{{y}^{2}}-4x-10y+16=0\]

    C) \[{{x}^{2}}+{{y}^{2}}-4x-10y+25=0\]

    D)  None of the above

    Correct Answer: C

    Solution :

    Let the centre of circle be (h, k). Then \[\sqrt{{{(h-2)}^{2}}+{{(k-3)}^{2}}}\]                 \[=\sqrt{{{(h-4)}^{2}}+{{(k-5)}^{2}}}\]                    ... (i) and                       \[k-4h+3=0\]                      ... (ii) From Eq. (i)                 \[-4h-6k+8h+10k=16+25-4-9\] \[\Rightarrow \]               \[h+k-7=0\]                                        ? (iii) On solving Eqs. (ii) and (iii), we get the centre of circle (2, 5). Now, radius\[=\sqrt{{{(2-2)}^{2}}+{{(5-3)}^{2}}}=2\] \[\therefore \]Required equation of circle is                 \[{{(x-2)}^{2}}+{{(y-5)}^{2}}={{2}^{2}}\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4x-10y+25=0\]


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