a/ (x2-1)(x2+2x)
=x4+2x3-x2-2x
b/ (2x-1)(3x+2)(3-x)
=(6x2+x-2)(3-x)
=-6x3+17x2+x-6
c/ (x+3)(x2+3x-5)
=x3+3x2-5x+3x2+9x-15
=x3+6x2+4x-15
d/ (x+1)(x2-x+1)
=x3+1 dùng HĐT
e/ (2x3-3x-1)(5x+2)
=10x4-15x2-5x+4x3-6x-2
=10x4+4x3-15x2-11x-2
f/ (x2-2x+3)(x-4)
=x3-2x2+3x-4x2+8x-12
=x3-6x2+11x-12
đừng làm tắt quá nhé, hơi thôi cũng đk