VITEEE 2012 Paper

Equation of family of concentric circles to
the circle x2+y2 + 6x + 8y- 5 = 0 is
x2+y2 + 6x+ 8y + λ = 0
which is similar to x2+y2 + 2gx + 2fy + c = 0
Thus, the point (-3,2) lies on the cirlce
x2+y2 + 6x + 8y + c = 0
∴ (−3)2+(2)2 + 6(-3) + 8 (2) + c = 0
⇒ 9 + 4 - 18 + 16 + c = 0
⇒ c = -11