How to isolate $n$ in the inequality $ 3n + 7n^3\gt c(17 + 34n^2) $? I have an equation 
$$ 3n + 7n^3\gt c\left(17 + 34n^2\right)
$$
and I want to turn this inequality into something like 
$$ n \gt c(\mbox{something that does not have}\ n)
$$
I don't know why but always get stumped at these types of questions. Any help would be appreciated, thanks.

What you want to do involves solving a cubic equation. It is possible but the solution is a so complicated formula that it is rather useless in most cases; the parameter $c$ makes things even tougher.
