Question
Question: The number of common tangents that can be drawn to the circles x<sup>2</sup>+y<sup>2</sup>–4x-6y-3 =...
The number of common tangents that can be drawn to the circles x2+y2–4x-6y-3 = 0 and x2+y2+2x+2y+1=0 is
A
1
B
2
C
3
D
4
Answer
3
Explanation
Solution
The two circles are
x2+y2-4x-6y-3 = 0 and x2+y2+2x+2y+1 = 0
Centres: C1 ≡(2, 3), C2 ≡(-1, -1)
Radii: r1 = 4 r2 = 1
We have, C1 C2 = 5 = r1 + r2, therefore there are 3 common tangents to the given circles