Réponse :
Exercice 1:
A = 9x² + 3x² = 12x²
B = 7x + 5x = 12x
C = -8 - 3x = impossible
D = 8x - 10x + 6x - 5 = 4x -5
E = -2x² -6x - 8 + 10x² + 2x + 3x = 8x² - 1x - 8
F = 4x² - 6x + 13 - 4x² + 15x - 6 = x² + 9 + 7
Exercice 2:
a. (8x + 5) + (6x - 2) = 8x*6x + 8x*(-2) + 5*6x + 5*(-2) = 48x² - 16x + 30x - 10 = 48x² + 14 - 10
b. (9x - 6) - (4x - 3) = 9x*4x - 9x*(-3) - 6*4x - 6*(-3) = 36x² - 27x - 24x + 18 = 36x² - 51 +18
Exercice 3:
1. (5x + 3 )(2x + 6) = 5x*2x + 5x*6 + 3*2x + 3*6 = 10x² + 30x + 6x + 18 = 10x² + 36x + 18
2. (4x + 8)(3x + 5) = 4x*3x + 4x*5 + 8*3x + 8*5 = 12x² + 20x + 24x + 40 = 12x² + 44x + 40
3. (6x - 4)(3x + 5) = 6x*3x + 6x*5 + 4*3x + 4*5 = 18x² + 30x + 12x + 20 = 18x² + 42x + 20
4. (-3 + 4x)(-2x - 4) = -3*(-2x) + (-3)*(-4) + 4x*(-2x) + 4x*(-4) = 6x + 12 - 8x² - 16x = -10 + 12 - 8x²
