[tex]1 - {9a}^{2} = (1 - 3a)(1 + 3a) \\ {m}^{2} - {a}^{2} = (m - a)(m + a) \\ - {n}^{2} + {b}^{2} = (b - n)(b + n) \\ {a}^{2} + {b}^{2} = {(a + b)}^{2} - 2ab \\ {a}^{2} - 16 {y}^{2} = (a - 4y)(a + 4y) \\ {81x}^{2} - {y}^{2} = (9x - y)(9x + y) \\ {100a}^{2} - {25b}^{2} = (10a - 5b)(10 a+ 5b) \\ {c}^{2} - {a}^{2} {b}^{2} = (c - ab)(c + ab)[/tex]