If you have an equation you are factoring to find the length of a leg of a right triangle, factor it to solve for x. If by some chance, one of those x-values is negative we can count that one out since length will never be negative. If you have 2 positive solutions, you may have to use some math to see if both of the lengths work according to pythagorean's theorem or if only one works. It depends upon what type of information you are given other than the quadratic.
