Question

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

center= (8,−2)
, radius=25

center= (4,−1)
, radius=5

center= (2,−8)
, radius=25

center= (−4,1)
, radius=5

Answer 1

(x^2 − 8x) → (x − 4)^2 − 16; (y^2 + 2y) → (y + 1)^2 − 1.

So (x − 4)^2 − 16 + (y + 1)^2 − 1 = 8 → (x − 4)^2 + (y + 1)^2 = 25.

Center = (4, −1), radius = 5.