Question

Using the equation x2+y2−8x+2y=8
, calculate the center and radius of the circle by completing the square.(1 point)

center= (−4,1)
, radius=5

center= (4,−1)
, radius=5

center= (2,−8)
, radius=25

center= (8,−2)
, radius=25

Answer 1

Start with x^2 + y^2 − 8x + 2y = 8.

Complete the square:
(x^2 − 8x) + (y^2 + 2y) = 8
(x − 4)^2 − 16 + (y + 1)^2 − 1 = 8
(x − 4)^2 + (y + 1)^2 = 25

So the center is (4, −1) and the radius is 5.