Réponse:
1) A= 3x-(2x+5)-7+(6x+8)
= 3x-2x-5-7+6x+8
= 7x-4
2) B= 4x(2x-3)
=8x²+12
C= (2x-5)(3x-7)
= 6x²+14x-15x+35
= 6x²-1x+35
3) D= 15x-20
= 5(3x-4)
E= (2x-1)(4x+3)+(2x-1)(7x-5)
=(2x-1)[(4x+3)+(7x-5)]
=(2x-1)(4x+3+7x-5)
=(2x-1)(11x-2)
