a) (2x-1)² - 16 = (2x-1)² - 4² = (2x-1 - 4)(2x-1 + 4) = (2x-5)(2x+3)
b) (1+3x)² - 25 = (1+3x)² - 5² = (1+3x - 5)(1+3x + 5) = (3x - 4)(3x+6) = 3·(x+2)(3x-4)
c) (5x-6)² - 36 = (5x-6)² - 6² = (5x-6 - 6)(5x-6 + 6) = 5x·(5x-12)
d) 49-(4x+5)² = 7² - (4x+5)² = (7 - 4x-5) (7+4x+5) = (2-4x)(4x+12) = 2·(1-2x) · 4(x+3) = 8·(1-2x)(x+3)
e) 64 - (1-7x)² = 8² - (1-7x)² = (8 - 1 + 7x)(8+1-7x) = (7+7x)(9-7x) = 7·(x+1)(9-7x)
f) 81 - (3-2x)² = 9² - (3-2x)² = (9 - 3+2x)(9+3-2x) = (6+2x)(12-2x) = 2·(x+3) · 2(6-x) = 4·(x+3)(6-x)
