Question

The number of common tangents to the circles $x^2+y^2-4x-6y-12=0$ and $x^2+y^2+6x+18y+26=0$

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (C)

3

Answer 2

$x^{2}+y^{2}-4 x-6 y-12=0$ $C_{1}(2,3) \,\,\,\,\,r_{1}=\sqrt{2^{2}+3^{2}+12}=5$ $x^{2}+y^{2}+6 x+18 y+26=0$ $C_{2}(-3,-9), r_{2}=\sqrt{3^{2}+9^{2}-26}=8$ $C_{1} \,C_{2}=\sqrt{(52+122)}=13$