[tex]formulele \: sunt \\ {(a + b)}^{2} = {a}^{2} + 2ab + {b}^{2} \\ {(a - b)}^{2} = {a}^{2} - 2ab + {b}^{2} \\ (a + b)(a - b) = {a}^{2} - {b}^{2} \\ a) \: {x}^{2} + 2x + 1 \\ b) \: {x}^{2} - 4x + 4 \\ c) \: {4x}^{2} + 12x + 9 \\ d) \: {9x}^{2} - 6x + 1 \\ e) \: {9x}^{2} - 1 \\ f) \: \frac{1}{9} {a}^{2} - {b}^{2} [/tex]
