Question

Find the center and radius for the circle, given the equation: x^2-14x+y^2+8=16

Answer 1

You can do this by completing the square

x^2 - 14x + y^2 + 8  = 16

(x - 7)^2 - 49 + (y + 4)^2 - 16  = 16

(x - 7)^2 + (y + 4)^2 =   16 + 16 + 49  =  81


so the center is at (7 , -4) and radius = sqrt81 = 9