Répondre :
A(x): 3(4x+7)+ 4(2x-9)
=12x+21+8x-36
=20x-15
B(x): 7x(2x-5)-x(2x-5)
=14x²-35x-2x²+5x
=12x²-30x
C(x): (5x+8)(2x-7)
=10x²+16x-35x-56
=10x²-19x-56
D(x):(2x+3)(5x-8)-(2x-4)(5x-1)
=10x²-x-34-10x²+22x-4
=21x-38
=12x+21+8x-36
=20x-15
B(x): 7x(2x-5)-x(2x-5)
=14x²-35x-2x²+5x
=12x²-30x
C(x): (5x+8)(2x-7)
=10x²+16x-35x-56
=10x²-19x-56
D(x):(2x+3)(5x-8)-(2x-4)(5x-1)
=10x²-x-34-10x²+22x-4
=21x-38