Q89 / 150 · MHT CET 2020 (15 Oct Shift 1) · Mathematics

If the radius of a circle $x^{2}+y^{2}-4 x+6 y-k=0$ is 5, then $\mathrm{k}=$

  • A
    $-12$
  • B
    $-25$
  • C
    $25$
  • Correct answer
    D
    $12$

Solution

Given equation of circle is $$ \begin{array}{l} x^{2}+y^{2}-4 x+6 y-k=0 \\ r \quad=\sqrt{4+9+k} \Rightarrow 5=\sqrt{13+k} \Rightarrow 13+k=25 \\ k=12 \end{array} $$

Hence, the correct answer is option: 'D'.

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