Question

Write an equation of the circle with center (4,5) and radius 9.

Answer 1

I'm going to write both of these because maybe you have a fill in the blank question. I don't know.

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

Simplify:

`(x-4)^2+(y-5)^2=81`

Explanation:

`(x-h)^2+(y-k)^2=r^2` is the equation of a circle with center (h,k) and radius r.

You are given (h,k)=(4,5) because that is the center.

You are given r=9 because it says radius 9.

Let's plug this in.

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

Simplify:

`(x-4)^2+(y-5)^2=81`

Answer 2

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

or

(x-4)^2 + (y-5)^2 =81

Explanation:

The equation for a circle is (x-h)^2 + (y-k)^2 = r^2

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

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

or

(x-4)^2 + (y-5)^2 =81