Réponse :
a) (-3x - 1)(4x - 3)
= -12x^2 - 4x + 9x + 3
= -12x^2 + 5x + 3
_______
b) (x - 2/3)^2
= x^2 - 2 (2/3)x + 4/9 ( (a - b)^2 = a^2 + b^2 - 2ab)
= x^2 - (4/3)x + 4/9
_______
c) x (7x + 9)(x - 1/3)
= x (7x^2 + 9x - (7/3)x - 9/3)
= x ( 7x^2 + (27/3)x - (7/3)x - 3)
= x (7x^2 + (20/3)x - 3)
= 7x^3 + (20/3)x^2 - 3x
_______
d) (x + y + z)^2
= x^2 + y^2 + z^2 + 2xy + 2xz + 2zy ( (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + . 2bc + 2ac)
