[tex]( \sqrt{3} + 5)( \sqrt{3} - 5) = 3 - 25 = - 22[/tex]
[tex](x + 2y)(x - 2y) = {x}^{2} - 4 {y}^{2} [/tex]
[tex](3b + c)(3b - c) = 9 {b}^{2} - {c}^{2} [/tex]
[tex]( \sqrt{5} - 2)( \sqrt{5} + 2) = 5 - 4 = 1[/tex]
((Am aplicat formula de calcul prescurtat
[tex](a - b)(a + b) = {a}^{2} - {b}^{2} [/tex]
))