Đáp án:
`d)` `-x^4+7x^3-11x^2+6x-5`
`e)` `x^4-7x^3+11x^2-6x+5`
`f)` `x^3-3x^2+3x-1`
`g)` `(x+y)^3`
Giải thích các bước giải:
`d)` `(5-x)(x^3-2x^2+x-1)`
`=5*x^3-5*2x^2+5*x-5*1-x*x^3-x*(-2x^2)-x*x-x*(-1)`
`=5x^3-10x^2+5x-5-x^4+2x^3-x^2+x`
`=-x^4+(5x^3+2x^3)+(-x^2-10x^2)+(5x+x)-5`
`=-x^4+7x^3-11x^2+6x-5`
`e)` `(x-5)(x^3-2x^2+x-1)`
`=x*x^3-x*2x^2+x*x-x*1-5*x^3-5*(-2x^2)-5*x-5*(-1)`
`=x^4-2x^3+x^2-x-5x^3+10x^2-5x+5`
`=x^4+(-2x^3-5x^3)+(x^2+10x^2)+(-x-5x)+5`
`=x^4-7x^3+11x^2-6x+5`
`f)` `(x-1)(x^2-2x+1)`
`=x*x^2-x*2x+x*1-1*x^2-1*(-2x)-1*1`
`=x^3-2x^2+x-x^2+2x-1`
`=x^3+(-2x^2-x^2)+(2x+x)-1`
`=x^3-3x^2+3x-1`
`g)` `(x^2-xy+y^2)(x+y)`
`=(x+y)(x^2-xy+y^2)`
`=(x+y)^3`
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