H = x*4 + x*(-2x) - 3*4 - 3*(-2x)
= 4x - 2x² - 12 + 6x
= -2x² + 10x - 12
puisque (a+b) (c+d) = ac + ad + bc + bd
Salut !
(x-3)(4-2x) = 4x-2x²-12+6x = -2x²+10x-12