Given equation of circles are S1≡x2+y2+2x+2y+1=0 and S2≡x2+y2−2x+2y+1=0 In circle S1, centre c1=(−1,−1), radius r1=√1+1−1=1 In circle S2, centre C2=(1,−1), radius r2=√1+1−1=1 Now, distance between two centre C1C2=√(−1−1)2+0 =2 Here, we see that C1C2=r1+r2 i.e., both circle touch externally. So, point of contact of circle S1 and S2 = Mid-point of C1 and C2=(