How would I find all reduced forms with discriminant -39? I tried setting it up:
$d = b^2-4ac = -39$ and was able to see that, for example, $1^2-4(2)(5)$ would work (since $-2 \leq 1 \leq 2 < 5$), but is there any way to find the other $a$'s, $b$'s, and $c$'s that would work?
Edit: We can bound $|a|$ by $\sqrt{\frac{-d}{3}}$. Is it just a case of checking all the combinations that work after that?