a math ...family of circle @ CE Q ...v urgent ...

The circle
C1 : x^2 + y^2 + 4x - 2y + 1 = 0 and
C2 : x^2 + y^2 + 10x + 4y + F = 0
intersect each other at two points P and Q , where the equation of the line PQ is x+y+3=0

(a) Find the value of F.
(b) M is an external point of C1 and C2. If M lies on the line PQ, show that the length of the tangent from M to C1 is equal to the length of tangent from M to C2.


( please state all the steps clearly )