1)
[tex]81c {}^{2} - 4 = (9c - 2)(9c + 2)[/tex]
since it is in the form of:
[tex]x {}^{2} - y {}^{2} = (x - y)(x + y)[/tex]
2)
[tex]75x {}^{2} - 27y {}^{2} = (5 \sqrt{3} x - 3 \sqrt{3} y)(5 \sqrt{3} x + 3 \sqrt{3} y)[/tex]
3)
[tex]z {}^{2} + 12z + 36[/tex]
[tex]z {}^{2} + 6z + 6z + 36[/tex]
[tex]z(z + 6) + 6(z + 6)[/tex]
[tex](z + 6)(z + 6)[/tex]
[tex](z + 6) {}^{2} [/tex]
4)
[tex]4f {}^{2} + 18f + 18f + 81[/tex]
[tex]2f(2f + 9) + 9(2f + 9)[/tex]
[tex](2f + 9)(2f + 9)[/tex]
[tex](2f + 9) {}^{2} [/tex]
5)
[tex]49a {}^{2} - 14a + 1[/tex]
[tex](7a - 1) {}^{2} [/tex]
6)
[tex]x {}^{4} - 16[/tex]
[tex](x {}^{2} - 4)(x {}^{2} + 4)[/tex]
