Question

How do you find the center and radius for `x^2+y^2-2x-8y+16=0`?

Answer 1

`C(1;4) and r=1`

Explanation:

Center coordinates are `(-a/2;-b/2)` where a and b are the coefficients for x and y, respectively, in the equation;

`r=1/2sqrt(a^2+b^2-4c)`

where c is the constant term

so

`r=1/2sqrt(4+64-4*16)`
`r=1/2sqrt(4)`
`r=1/2*2=1`