If \(x^2+y^2+6 x+2 k y+25=0\) to touch \(Y\)-axis, then \(k=\)
If \(x^2+y^2+6 x+2 k y+25=0\) to touch \(Y\)-axis, then \(k=\)
\pm 20
\(-1,-5\)
\pm 5
4
Solution
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 \(=\sqrt{9+k^2-25}\)
\(\Rightarrow \sqrt{k^2-16}=3 \Rightarrow k^2=25 \Rightarrow k= \pm 5\)