Question

How do you write an equation of a circle with center at origin and r=3?

Answer 1

The standard form is:
`(x - h)^2 + (y - k)^2 = r^2`
where (h,k) is the center and r is the radius.
Your center is at `(0,0)` and the radius, `r = 3`
`(x - 0)^2 + (y - 0)^2 = 3^2`