Show that $\displaystyle x^2 + 3x + 2 $ has four zeros in $\displaystyle Z_{6}$.

$\displaystyle x^2 + 3x + 2 = (x+2)(x+1)$, by the factor theorem, -1 and -2 are zeros of the poly.

However, -2 = 4 and -1 = 5 in $\displaystyle Z_{6}$. But what are the other two?

Thanks.