Bonjour,
Exercice 2 :
A = 8x + x (10 - x)
B = 10x + x (8 - x)
1 . Pour A = B pour x = 3 et x = 7
A = 8 × 3 + 3 (10 - 3)
A = 24 + 3 × 10 + 3 × (-3)
A = 24 + 30 - 9
A = 54 - 9
A = 45
B = 10x + x (8 - x)
B = 10 × 3 + 3 × 8 + 3 × (-3)
B = 30 + 24 - 9
B = 24 - 9
B = 45
Donc l'égalité est bonne pour x = 3
A = 8x + x (10 - x)
A = 8 × 7 + 7 × 10 + 7 × (-7)
A = 56 + 70 - 49
A = 126 - 49
A = 77
B = 10x + x (8 - x)
B = 10 × 7 + 7 × 8 + 7 × (-7)
B = 70 + 56 - 49
B = 126 - 49
B = 77
Donc l'égalité est bonne pour x = 7
A = 8x + x (10 - x)
A = 8 × x + x × 10 + x × (-x)
A = 8x + 10x - x²
A = - x² + 18x
B = 10x + x (8 - x)
B = 10 × x + x × 8 + x × (-x)
B = 10x + 8x - x²
B = - x² + 18x
