Question

If length of common chord of two circles x² + y² + 8x + 1 = 0 and x² + y² + 2my –1 = 0 is $2\sqrt{6}$, then value of m are

• A. ±2
• B. ±3
• C. ±4
• D. None of these

Answer 1

Answer: (B)

±3

Answer 2

Common chord is S₁ – S₂ = 0

4x – my + 1 = 0

\ AC =$\sqrt{15}$

AM = $\frac{AB}{2}$= $\sqrt{6}$

\ CM = 3

\ $\frac{| - 16 + 1|}{\sqrt{16 + \mu^{2}}}$= 3

Ž m = ±3