Question

Determine the center and radius of the following circle equation:

x^2 + y^2 – 18x + 18y + 137 = 0

Answer 1

x^2-18x+y^2+18y+137=0

express both x and y term in completed square form

(x-9)^2 -81+(y+9)^2-81+137=0

(x-9)^2+(y+9)^2-25=0

(x-9)^2+(y+9)^2=5^2

here the x coordinate of the centre is +9

y coordinate is -9(the negative value of the value associated with the x and y square brackets)

radius=5