Consider the equation of circles. x2+y2−14x+6y+33=0 Its centre is (7,-3) and radius is r1=5 . And, x2+y2+30x−2y+1=0 Its centre is (-15,1) and radius is r2=15 The point C1 that divides the center of circle externally in the ratio 1: 3 is calculated as, C1=(
−15+21
4
,
1−9
4
) =(
3
2
,−2) The point C2 that divides the center of circle externally in theratio 1: 3 is calculated as, C2=(
−15−21
1−3
,
1+9
1−3
) =(
−36
−2
,
10
−2
) =(18,−5) Now, the equation of circle with diameter as C1C2 is given by, (x−