[tex]bonjour \\ a = (x - 9) {}^{2} \\ a = x {}^{2} - {2}x \times 9 + 9 {}^{2} \\ a = x {}^{2} - 18x + 81 \\ \\ b = (x + 15) {}^{2} \\ b = x {}^{2} + 2x \times 15 + {15}^{2} \\ b = {x}^{2} + 30x + 225 \\ \\ c = (4x + 7)(4x - 7) \\ c = (4x) {}^{2} - 7 {}^{2} \\ c = 16 {x}^{2} - 49 \\ \\ d = (x - 3)(x - 2) \\ d = x \times x - 2x - 3x - 3 \times ( - 2) \\ d = {x}^{2} - 2x - 3x + 6 \\ d = {x}^{2} - 5x + 6[/tex]
