7. The circle \(C\) has centre \(( - 1,6 )\) and radius \(2 \sqrt { 5 }\).
- Find an equation for \(C\).
The line \(y = 3 x - 1\) intersects \(C\) at the points \(A\) and \(B\).
- Find the \(x\)-coordinates of \(A\) and \(B\).
- Show that \(A B = 2 \sqrt { 10 }\).