Question

What is the radius for a circle whose equation is x^2+y^2=64

Answer 1

8 is the radius.

Explanation:

The standard form of a circle is
`(x-h)^2+(y-k)^2=r^2`.

However, I like to call it center-radius form because it tells us the center and the radius.

The center is
`(h,k)` and the radius is
`r`.

So your equation is
`(x-0)^2+(y-0)^2=8^2`.

So the center for this circle is (0,0) and the radius is 8.

If it wasn't so obvious that
`8^2` is 64 then you could have entered
`√(64)` in your calculator to get 8.