Question
Question: If circle x<sup>2</sup> + y<sup>2</sup> + 6x + 8y + a = 0 bisects circumference of circle x<sup>2</s...
If circle x2 + y2 + 6x + 8y + a = 0 bisects circumference of circle x2 + y2 + 2x – 6y – b = 0 then a + b =
A
38
B
– 38
C
42
D
– 42
Answer
– 38
Explanation
Solution
Line S1 – S2 = 0 i.e. 4x + 14 y + (a + b) =0
passes through center of S2 = 0
[Centre of S2 = (–1, 3)]
Ž – 4 + 42 + (a + b) = 0
Ž a + b = – 38