A=x(2x-1)-5(2x-1)(x+3)
=(2x-1)[x-5(x+3)]
=(2x-1)(x-5x-15)
=(2x-1)(-4x-15)
B=
(x+3)au carré-(2x+1)au carré
=[(x+3)+(2x+1)][(x+3)-(2x+1)]
=(x+3+2x+1)(x+3-2x-1)
=(3x+4)(-x+2)
C=
4xau carré-(x-3)au carré
=[2x+(x-3)][2x-(x-3)]
=(2x+x-3)(2x-x+3)
=(3x-3)(x+3)
