Correct Answer - Option 3 : √6
Concept:
The general second degree equation of a circle in x and y is given by: x2 + y2 + 2gx + 2fy + c = 0 with centre (-g, -f) and radius
\(\rm r = \sqrt {{g^2} + {f^2} - c} \)
Calculation:
Given: 3x2 + 3y2 + 12x + 12y + 6 = 0
⇒ 3 × (x2 + y2 + 4x + 4y + 2) = 0
⇒ x2 + y2 + 4x + 4y + 2 = 0 are equation of circle with centres C and radius r
By comparing the equation of the circle with the equation x2 + y2 + 2gx + 2fy + c = 0 we get
g = 2, f = 2 and c = 2
As we know, radius = \(\rm r = \sqrt {{g^2} + {f^2} - c} \)
\(\rm r = \sqrt {{4} + {4} - 2} \)
r = √6 unit
