Answer:
[tex]1) {n}^{2} - 81 \\ (n - 9)(n + 9)[/tex]
[tex] 2) \: \: {a}^{2} - 121 \\ (a - 11)(a + 11)[/tex]
[tex]3) \: \: {n}^{2} - 16 \\ (n - 4)(n + 4)[/tex]
[tex]4) \: \: 9 {x}^{2} - 144 \\ {3}^{2} {x}^{2} - {12}^{2} \\ (3x - 12)(3x + 12)[/tex]
[tex]5) \: 2 {x}^{2} - 9 \\ (2x - 3)(x + 3)[/tex]
[tex]6) \: \: 4 {w}^{2} - 9 \\ {2}^{2} {w}^{2} - {3}^{2} \\ (2w + 3)(2w - 3)[/tex]
[tex]7) \: \: 4 {n}^{2} - 1 \\ {2}^{2} {n}^{2} - {1}^{2} \\ (2n + 1)(2n - 1)[/tex]
[tex]8) \: \: 1 - 16 {x}^{2} \\ {1}^{2} - {4}^{2} {x}^{2} \\ (1 - 4x)(1 + 4x)[/tex]
[tex] 9) \: \: {x}^{2} - {y}^{2} \\ (x - y)(x + y)[/tex]
[tex]10) \: \: 9 - {c}^{2} \\ {3}^{2} - {c}^{2} \\ (3 - c)(3 + c)[/tex]
[tex]11) \: \: {n}^{2} - 25 \\ {n}^{2} - {5}^{2} \\ (n + 5)(n - 5)[/tex]
[tex]13)49 - 4 {a}^{2} \\ {7}^{2} - {2}^{2} {a}^{2} \\ (7 - 2a)(7 + 2a)[/tex]
[tex]14) {a}^{2} {b}^{2} - {c}^{4} \\ (ab - {c}^{2} )(ab + {c}^{2} )[/tex]
[tex]15) \: \: 4 {x}^{2} {y}^{2} - 9 {z}^{2} \\ {2}^{2} {x}^{2} {y}^{2} - {3}^{2} {z}^{2} \\ (2xy - 3z)(2xy + 3z)[/tex]
hope this helps
sorry, I don't know how solve the 12th one.
thanks.
