Question 372624
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Hi,
The standard equation of a circle with center C(h,k) and radius r is :
{{{(x - h)^2 + (y - k)^2 = r^2}}}
Find the radius
completing the squares
x^2+y^2+12x+8y+16=0
(x+6)^2 + (y+4)^2 -36 -16 +16 = 0
(x+6)^2 + (y+4)^2 = 36 = 6^2
radius is 6, the center of the circle (-6,-4)

{{{drawing(500,500, -15,4,-15,4,grid(1),circle(-6,-4,6), circle(-6,-4,.15), line(-6,-4,0,-4),locate(-6,-4,C),locate(-3,-4,r))}}}