Question

If 3x² + 2lxy + 3y² + (6 – l)x + (2l – 6)y – 21 = 0 is the equation of a circle, then its radius is-

• A. 1
• B. 3
• C. 2$\sqrt{2}$
• D. None of these

Answer 1

Answer: (B)

3

Answer 2

3x² + 2lxy + 3y² + (6 –l)x + (2l –6)y –21 = 0

coefficient of xy = 0 l = 0

On putting l = 0; x² + y² + 2x –2y – 7 = 0;

Radius = $\sqrt{1 + 1 + 7}$= 3