bonjour ;)
exercice 1
À = (x-5)(6-x) = 6x - x°2 - 30 + 5x = 11x - x°2 - 30
B = (2x+3)(x-5) = 2x°2 - 10x + 3x - 15 = 2x°2 - 7x -15
C=(-3x+2)(2x-3) + (3x-1)(3x+1) = (-6x°2+9x+4x-6) + (9x°2 - 1) = -6x°2 + 13x - 6 + 9x°2 - 1 = 3x°2 + 13x - 7e
D = 5 - (-4x°2+5x+7) + (-6x°2-2x-8) = 5 + 4x°2 - 5x - 7 - 6x°2 - 2x - 8 = -10 - 2x°2 - 7x
exercice 2 :
E = 6 + 3x - 4 (x-2y)
x = -4 et y = -3
6 + 3×(-4) -4 (-4-2×(-3))
6 - 12 - 4 (-4+6)
-6 + 16 - 24
-14
