bjr
double distributivité
(a+b) (c+d) = ac + ad + bc + bd
donc
(2x - 3) (5x - 4) = 2x * 5x + 2x * (-4) - 3 * 5x - 3 * (4)
on calcule
= 10x² - 8x - 15x + 12
= 10x² - 23x + 12
et
3x (2x - 7) = 3x * 2x + 3x * (-7) = 6x² - 21x
puisque k (a + b) = k*a + k*b
