Réponse :
a) 2 (3+y) = 2 × 3 + 2 × y = 6+2y
b) -5 ( x-y) = -5 × x -5 × (-y) = -5x+5y
c) -3 ( -2x+y) = -3 × (-2x) - 3 × y = 6x - 3y
d) x ( -4 - y) = x × (-4) + x × (-y) = -4x - xy
e) 2x ( x - y + 4) = 2x × x + 2x × (-y) + 2x × 4 = 2x² - 2xy + 8x
f) ( -4 + x) × 5= -4 × 5 + x × 5 = -20 + 5x = 5x - 20
g) - ( 3 - x ) = -3 + x
h) + ( -1 + x) = -1 = x
Explications :
k(a + b) = ka + kb
k(a − b) = ka − kb
