Here's the question you clicked on:
simplybeyoutiful
How can you tell when a quadratic equation has two identical, rational solutions? A) when the radicand is negative B) when b in the quadratic formula is greater than the radicand C) when the radicand equals zero D) when the radicand is not a perfect square
This is a definitions thing you should memorize: :-) http://en.wikipedia.org/wiki/Discriminant#Quadratic
FYI, "multiplicity" means it's a repeated root, in this case a double-root. Think of it as being cloned or whatever, multiple identical solutions.
hint there are two identical roots when \[b^2 - 4ac = 0\] from the quadratic formula does that help?