At least for myself and the original poster, the thread at
Finding roots of polynomials, negative square root
does not render correctly. From OPs post:
"yep tried reloading a few times, the explanation cuts off "there is one solution (the repeated root) and if b^2-4ac" (so you can see part of the markup is probably at fault as i assume this is mid sentence) - c'mon admins help us out! – Aran Mulholland 16 hours ago"
Interestingly it works fine on the preview page, and as far as I know the latex is correct.
Edit: Original is fixed now. The error occurs when using the typing the $\lt$ as opposed to using the latex \lt.
$a \lt b$ vs $a < b$