I use the railroad method so here's how I would solve it: 4 x 25 = 100 10 x 10 = 100, 10 + 10 = 20 (x +10/4)(x + 10/4) (x + 5/2)(x + 5/2) The answer should be: (2x + 5)(2x + 5)
It can be checked: 2x x 2x = 4x^2 2x x 5 = 10x 5 x 2x = 10x 5 x 5 = 25 4x^2 + 20x + 25
