Bonjour,
double distributivité.....
(x+9)(x+5) = x*x + x*5 + 9*x + 9*5 = x²+14x+45
(x+4)(x-9) = x*x - x*9 + 4*x - 4*9 = x²-5x-36
(7x+2)(3x+5) = 7x*3x + 7x*5 + 2*3x + 2*5 = 21x²+41x+10
(3x-4)(5x+1) = 3x*5x + 3x*1 - 4*5x - 4*1 = 15x²-17x-4
(7x-8)(4x-5) = 7x*4x - 7x*5 - 8*4x + 8*5 = 28x²-67x+40
(8x-3)(-6x-5) = 8x*(-6x) - 8x*5 + 3*6x + 3*5 = -48x²-22x+15
