6. a) (5x-2y)(x2-xy+1)
=5x3-5x2y+5x-2x2y+2xy2-2y
=5x3-7x2y+2xy2+5x-2y
b) (x-1)(x+1)(x+2)
= (x2+x-x-1)(x+2)
=(x2-1)(x+2)
=x3+2x2-x-2
c) 1/2x2y2(2x+y)(2x-y)
=(x3y2+1/2x2y3)
(2x-y)
=2x4y2-1/2x2y4
7. a) (1/2x-1)(2x-3)
=x2-3/2x-2x+3
=x2-7/2x+3
b) (x-7)(x-5)
=x2-5x-7x+35
=x2-12x+35
c)
(x-1/2)(x+1/2)(4x-1)
=(x2+1/2x-1/2x-1/4)(4x-1)
=(x2-1/4)(4x-1)
=4x3-x2-x+1/4
8. a) (x-1)(x2+x+1)=x3-1
óx3+x2+x-x2-x-1=x3-1
óx3-1=x3-1
b) (x3+x2y+xy2+y3)(x-y)=x4-y4
óx4+x3y+x2y2+xy3-x3y-x2y2-xy3-y4=x4-y4
óx4-y4
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