Bonjour !
exercice 1 :
x = 2:
A = 3x + 7 = 3*2 + 7 = 6 + 7 = 13
B = 2x² + 5x - 3 = 2*2² + 5*2 - 3 = 8 + 10 - 3 = 15
x = -3:
A = 3 * (-3) + 7 = -9 + 7 = -2
B = 2*(-3)² + 5*(-2) - 3 = 2*9 -10 - 3 = 18 - 13 = 5
exercice 2:
A = 5x + 3 + 2x - 1 = 7x - 2
B = 4x² - 5 - 3x - x - x² + 5 = 3x² - 4x
C = 4x + 7 - (2x + 1) = 4x + 7 -2x - 1 = 2x - 6
exercice 3:
A = 3(2x + 1) = 6x + 3
B = 2x(1 - 2x) = 2x - 4x²
C = (2 + x)(3x + 5) = 6x + 3x² + 10 + 5x = 3x² + 11x + 10
D = (3 - 5x)(3 + 5x) = 3² - (5x)² = 9 - 25x² (identité remarquable, a² - b² = (a-b)(a+b) )
E = (x + 2)² = x² + 4x + 4 (identité remarquable, (a+b)² = a² +2ab + b² )
F = (4 + x)² - (2 - x)² = 16 + 8x + x² - 4 + 4x - x² = 12 + 12x
exercice 4 :
1)
2:
2+5 = 7
7*4 = 28
28-20 = 8
10:
10+5 = 15
15*4 = 60
60-20 = 40
2)
x
(x+5) * 4 - 20 = 4x + 20 - 20 = 4x
le programme multiplie en effet le nombre de départ par 4.
voilà, j'espère t'avoir aidé.
