5 Two points have coordinates \(A ( 5,7 )\) and \(B ( 9 , - 1 )\).
- Find the equation of the perpendicular bisector of \(A B\).
The line through \(C ( 1,2 )\) parallel to \(A B\) meets the perpendicular bisector of \(A B\) at the point \(X\).
- Find, by calculation, the distance \(B X\).