(2x + 5)2 - (2x - 5)2 = [(2x)2 + 2(2x)(5) + (5)2] - [(2x)2 - 2(2x)(5) + (5)2]                            = [4x2 + 20x + 25] - [4x2 - 20x + 25]                            = 4x2 + 20x + 25 - 4x2 + 20x - 25                            = (4x2 - 4x2 ) + (20x + 20x) + (25 - 25)                            = 0 + 40x + 0                            = 40x