Question

Find the center and radius of a circle defined by the equation x^2+yy^2+4x-8y+13=0

Answer 1

hello : 
x²+y²+4x-8y +13 = 0
(x² +4x) +(y² -8y )+13 = 0
(x²+4x+4) -4 +(y-8y +16) -16 +13 = 0
(x+2)² +(y -4)² = 7
the center is : (-2 , 4) and radius √7