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The equation of a circle is \(3x^{2} + 3y^{2} + 6x - 12y + 6...

The equation of a circle is 3x2+3y2+6x12y+6=0. Find its radius

A.

1

B.

3

C.

11

D.

6

Correct answer is B

The equation of a circle is given as (xa)2+(yb)2=r2

Expanding this, we have x2+y22ax2by+a2+b2=r2

Comparing with the given equation, 3x2+3y2+6x12y+6=0x2+y2+2x4y+2=0 (making the coefficients of x2 and y2 = 1 , we get that

2a=2a=1

2b=4b=2

r2a2b2=2

r = \sqrt{3}