Bonjour,
a) (2x+9)(5x-3)+(5x-3)²
= 10x²-6x+45x-27+25x²-30x+9
= 35x²+9x-18
b) (2x+9)(5x-3)+(5x-3)²
= (2x+9)(5x-3)+(5x-3)(5x-3)
= (5x-3)[(2x+9)+(5x-3)]
= (5x-3)(7x+6)
c) x = -3 ⇒ (5x-3)(7x+6) = (5(-3)-3)(7(-3)+6) = (-15-3)(-21+6) = 270
d) (5x-3)(7x+6) = 0 ⇒ 5x-3=0 ou 7x+6=0
⇒ 5x = 3 ou 7x = -6
⇒ x = 3/5 ou x = -6/7
