Hi,

Can anyone give me a hand with the following problem please?

For what range of values of k does:x^2+y^2+4kx-2ky-k-2+0

represent a circle?

I have tried using the radius formula :-

Sqrrt (-2k)^2 + (k)^2 -(k-1)

Sqrrt 4k^2 + k^2 -k+1

Sqrrt 5k^2 -k+1......

Thanks

Cromlix