Question 372701
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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  
x^2+y^2+12x+4y+76=0
completing the squares
x^2+12x +   y^2+4y       + 76=0
(x+6)^2 + (y+2)^2 -36 -4 + 76 = 0
(x+6)^2 + (y+2)^2 = 36 = 6^2
radius = 6, center (-6,-2)
{{{drawing(500,500, -15,5,-15,5,grid(1),circle(-6,-2,6), circle(-6,-2,.15), 
line(-6,-2,0,-2),locate(-6,-2,C),locate(-3,-2,r))}}}