Factoring Quadratic Expressions Using X-Box Method. This worksheet has a step by step example on how to use the x-box (aka: diamond box or just box) method along with a page of 14 practice problems and another page of blank problems that have the x and the box drawn out. I feel that the x-box method is the best way to teach students factoring. Oh, and make sure you explain what each letter stands for: F = First term, M = Middle term, L = Last term, a and b are just the factors of F x L and t