Question

Find the radius of the circle whose equation is x² - 10x + y² - 10y = -1 a)1 b)7 c)49

Answer 1

After completing the square, the right side of the equation is always the radius squared, so you just need to square root the right side.

(x - 5)² + (y - 5)² = 49

Square root of 49 = 7.

Your answer is 7.