Bonjour,
A = (4x + 7) (3x - 5)
A = 12x² - 20x + 21x - 35
A = 12x² + x - 35
B = (- 2x - 4) (5x - 7)
B = - 10x² + 14x - 20x + 28
B = - 10x² - 6x + 28
1) 7x + 8 = 4x - 10
7x - 4x = - 10 - 8
3x = - 18
x = - 18/3
x = - 6
2) - 9x + 24 = 15 + 50
- 9x = 15 + 50 - 24
- 6x = 41
x = - 41/6