SVP AIDEZ MOI A L'EXERCICE 18,19 !!!!!!

Exercice 18 : 

1) D = (x + 5) (2x - 3) - 3 (4x + 1)
D = x * 2x + x * (- 3) + 5 * 2x + 5 * (- 3) - 3 * 4x - 3 * 1
D = 2x² - 3x + 10x - 15 - 12x - 3
D = 2x² - 5x - 18

2) Pour x = 1

D = 2x² - 5x - 18
D = 2 * 1² - 5 * 1 - 18
D = 2 * 1 - 5 - 18
D = 2 - 5 - 18
D = - 21

Exercice 19 :

E = 7 (3 - x) + (x + 4) (x - 5)
E = 7 * 3 + 7 * (- x) + x * x + x * (- 5) + 4 * x + 4 * (- 5)
E = 21 - 7x + x² - 5x + 4x - 20
E = x² - 8x + 1

2) Pour x = 0 

E = x² - 8x + 1
E = 0² - 8 * 0 + 1
E = 0 - 0 + 1
E = 1