Réponse:
[tex]a = (x - 2)(x + 2) \\ = {x}^{2} - 4[/tex]
[tex]b = (5 - y)(5 + y) \\ = 25 - {y}^{2} [/tex]
[tex]c = (3x + 5)(3x - 5) \\ = 9 {x}^{2} - 25[/tex]
[tex]d = (10 - 7z)(10 + 7z) \\ = 100 - 49 {z}^{2} [/tex]
[tex]e = (5 + 4g)(5 - 4g) \\ = 25 - 16 {g}^{2} [/tex]
[tex]f = (2.1x - 3)(2.1x + 3) \\ = 4.41 {x}^{2} - 9[/tex]
