Question

5. Which equation is of a circle that has a center at

(3,-2) and a radius of 9?
A (x + 3)2 + (y - 2)2 = 9
B (x + 3)2 + (y - 2)2 = 81
C (x - 3)2 + (y + 2)2 = 9
D (x - 3)2 + (y + 2)2 = 81

Answer 1

`\large\boxed{D.\ (x-3)^2+(y+2)^2=81}`

Explanation:

The standard form of an equation of a circle:

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

(h, k) - center

r - radius

We have the center at (3, -2) and the radius r = 9. Substitute:

`(x-3)^2+(y-(-2))^2=9^2\\\\(x-3)^2+(y+2)^2=81`