Question

What is the center and radius of the circle with equation `x^2 + y^2 – 8x – 20y + 80 = 0`?

Answer 1

Centre`=(4,10)` radius`=6`

Explanation:

It's enough to complete the squares....
`x^2-8x+16+y^2-20y+100-16-100+80=0`
`(x-4)^2+(y-10)^2=36`