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AP EAMCET · Maths · Circle

If \(x^2+y^2+6 x+2 k y+25=0\) to touch \(Y\)-axis, then \(k=\)

  1. A \pm 20
  2. B \(-1,-5\)
  3. C \pm 5
  4. D 4
Verified Solution

Answer & Solution

Correct Answer

(C) \pm 5

Step-by-step Solution

Detailed explanation

Given circle \(x^2+y^2+6 x+2 k y+25=0 \text { touches } Y \text {-axis }\) and here centre is \((-3,-k)\) so radius \(=3\) units Also radius \(=\sqrt{9+k^2-25}\) \(\Rightarrow \sqrt{k^2-16}=3 \Rightarrow k^2=25 \Rightarrow k= \pm 5\)