Question

What is it in standard form?

The center is (0,0) and a point on the circle is (4,0)

Answer 1

`x^2+y^2=16`

Explanation:

The standard form for a circle with center `(h,k)` and radius `r` is
`(x-h)^2+(y-k)^2=r^2`.

In your case, `h=0` and `k=0`. All you need now is your radius, `r`. You find that by looking at the distance between the center and any point on the circle. The point you are given is `(4,0)`. That is `4` units away from the center (`(0,0)`)

So now you have
`(x-0)^2+(y-0)^2=4^2`

This simplifies to
`x^2+y^2=16`