Question

Which of the following is the equation of a circle with center (4, -1) and radius of 8?

(x - 4)2 + (y + 1)2 = 64

(x + 4)2 + (y - 1)2 = 64

(x - 4)2 + (y + 1)2 = 8

(x + 4)2 + (y - 1)2 = 8

Answer 1

the 3rd one

Answer 2

The equation of a circle is (x-x1)^2 + (y-y1) = r^2 where (x1,y2) is the center and r is the radius. Plugging 4 in for x, -1 in for y, and 8 in for r, you get:
(x-4)^2 + (y+1)^2 = 64,

so the third choice is correct.

Answer 3

the 1st one

Answer 4

My bad, the first one is correct, sorry.

Answer 5

ah yes...the 64!