You just honoured your nick and got a bit lazy while writing a lot of stuff.
And besides you say yourself you are doing things the wrong way when you do it, which is always good.
Anyway, larger the n the more the squared term dominates, but with early levels it's probably better to use the exact form. Which is like secondary school material. In general a*x^2 + b*x + c = 0 => x = (-b +-sqrt(b^2 - 4*a*c))/(2*a) if someone doesn't remember anymore. (Really hope I got that right)