9. The circle \(C\) has equation
$$x ^ { 2 } + y ^ { 2 } + 10 x - 6 y + 9 = 0$$
- Find the coordinates of the centre of \(C\).
- Find the radius of \(C\).
The point \(P ( - 2,7 )\) lies on \(C\).
- Find an equation of the tangent to \(C\) at the point \(P\).
Write your answer in the form \(a x + b y + c = 0\), where \(a , b\) and \(c\) are integers.