Find the equation of the circle passing through the center of the circle x^2 + y^2 + 8x + 10y-7 =0 and is concentric with the circle 2x^2 +2y^2 -8x- 12y-9 =0?
How do I prove, the chord of contact of pair of tangents to circle: [math]x^2+y^2=1[/math] drawn from any point on line: [math]2x+y=4[/math] passes through a fixed point?