Find the equation of family of circles passing through the point of intersection of the circles x2 + y2 − 2x − 4y − 4 = 0 and x2 + y2 − 10x − 12y + 40 = 0 and whose radius is 4.
Find the equations of transverse common tangents for two circles
x2 + y2 + 6x − 2y + 1 =0 , x2 + y2 − 2x − 6y + 9 = 0