The radius of the circle represented by equation 3x2 + 3y2 + λxy + 9x + (λ – 6) y + 3 = 0 is
Given that the equation of the circle is:
⇒ 3x2 + 3y2 + λxy + 9x + (λ - 6)y + 3 = 0 ...... (1)
Comparing with the standard equation of circle:
⇒ x2 + y2 + 2ax + 2by + c = 0
We get
⇒ λ = 0
Substituting λ value in (1), we get
⇒ 3x2 + 3y2 + 0xy + 9x + (0 - 6)y + 3 = 0
⇒ 3x2 + 3y2 + 9x - 6y + 3 = 0
⇒ x2 + y2 + 3x - 2y + 1 = 0
We know that for a circle x2 + y2 + 2ax + 2by + c = 0
⇒ Centre = (- a, - b)
⇒ Radius =
⇒ Radius (r) =
⇒
⇒
⇒
∴The correct option is (a)