Question

Which equation represents a circle with a center at (-4.9) and a diameter of 10 units?

(x – 9)2 + (y + 4)2 = 25
(x + 4)2 + (y - 9)2 = 25
(x - 9)2 + (y + 4)2 = 100
(x + 4)2 + (y - 9)2 = 100

Answer 1

(x+4)^2 + (y-9)^2 = 25

Explanation:

We can write the equation of a circle as

(x-h)^2 + (y-k)^2 = r^2

where (h,k) is the center and r is the radius

We know the diameter is 10 so the radius is 1/2 *10 = 5

(x- -4)^2 + (y-9)^2 = 5^2

(x+4)^2 + (y-9)^2 = 25