The circle C has equation
x2 + y2 – 6x + 4y = 12
(a) Find the centre and the radius of C.
(5)
The point P(–1, 1) and the point Q(7, –5) both lie on C.
(b) Show that PQ is a diameter of C.
(2)
The point R lies on the positive y-axis and the angle PRQ = 90°.
(c) Find the coordinates of R.
(4)
need help in part C with explanation plz