Question

What are the center and radius of the circle defined by the equation ?

A. Center (3, -4); radius 2
B. Center (-3, 4); radius 2
C. Center (-3, 4); radius 4
D. Center (3, -4); radius 4

Answer 1

it might be B im not sure

Answer 2

x^2 - 6x + y^2 + 8y + 21 = 0
(x - 3)^2 - 9 + (y + 4)^2 - 16 = -21

(x - 3)^2 + (y + 4)^2 = -21 + 9 + 16 = 4

so center is at (3,-4) and radius = sqrt4 = 2

Answer is A