Explications étape par étape:
[tex]1.(x +1 2) = x + 12[/tex]
[tex]2.(3x + 1)(3x - 1) = {(3x)}^{2} - {1}^{2} = 9x ^{2} - 1[/tex]
[tex]3.(2x - 5) = 2x - 5[/tex]
[tex]4.(x + 3)(x + 5) = {x}^{2} + 5x + 3x + 15 = {x}^{2} + 8x + 15[/tex]
[tex]5.2x(x - 4) + (3x - 7)(x + 5) = 2 {x}^{2} - 8x + 3 {x}^{2} + 15x - 7x - 35 = 2 {x}^{2} - 15x + 15x + 3 {x}^{2} - 35 = 5 {x}^{2} - 35 = 5( {x}^{2} - 7)[/tex]