Question

What is the radius of a circle whose equation is x2 + y2 – 10x + 6y + 18 = 0?

____ units

Answer 1

answer is 4 units

Explanation:

Answer 2

one way is the complete the square to convert this formula to the standard for form where RHS = radius^2

x^2 - 10x + y^2 + 6y = -18
(x-5)^2 - 25 + (y+3)^2 - 9 = -18
(x-5)^2 + (Y+3)^2 = -18 + 25 + 9 = 16

SO r^2 = 16


THE RADIUS = r = 4 UNITS