Question

What is the radius of the circle given by the equation below?

x2 - 4x + y2 - 4y - 73 = 0

Answer 1

hello :
(x² - 4x )+( y² - 4y) - 73 = 0
(x² - 4x+4-4 )+( y² - 4y+4-4) - 73 = 0
(x² - 4x+4)-4 +( y² - 4y+4)-4 - 73 = 0
(x-2)² +(y-2)² = 9²

the radius is : 9