Bonsoir j'ai du mal a cet exercice pouvez vous m'aidez ? Je vous remercie d'avance A=-5x(9x²+4) B=2(6x-4)-(8x²+2x-8) C=(7x+5)(4x+8) D=(7x-5)(8x+6) E=(2:3x-8)(7-

A=-5x(9x²+4)
=-45x³-20x

B=2(6x-4)-(8x²+2x-8)
=12x-8-8x²-2x+8
=-8x²+10x

C=(7x+5)(4x+8)
=28x²+56x+20x+40
=28x²+76x+40

D=(7x-5)(8x+6)
=56x²+42x-40x-30
=56x²+2x-30

E=(2/3x-8)(7-4/5x)
=14/3x-8/15x²-56+32/5x
=-8/15x²+70/15x+96/15x-56
=-8/15x²+166/15x-56

A=-5x(9x²+4) = 45 x^3 +20x
B=2(6x-4)-(8x²+2x-8) = 12x - 8 - 8x^2 -2x +8 = - ( 8x^2 - 10x ) = -2 x (4x-5)
C=(7x+5)(4x+8)= 28x^2+56x+20x+40 = 28x^2 + 76x +40 = 4 (7x^2 +19x +10)
D=(7x-5)(8x+6) = 56 x^2+42x -40x -30 = 56x^2 +2 x -30 = 2 ( 28x^2 +2 x -15)
E=(2:3x-8)(7-4:5x) = 14/3x - 2/3x 4/5x - 56 + 32/5x= 14 5x/15x - 8/15x -56 + 96x/15x =
(70 +96 -8)x/ 15 x -56 = 158/15 - 56*15/15 =(158-840)/15 = -682/15 = -45 - 7/15