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`a,`
`A=(x+2)(x^2 - 2x + 4) - x^3 +2`
`->A=x^3 +2^3 -x^3+2`
`->A=x^3 + 8 -x^3+2`
`->A=10`
Vậy `A=10`
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`b,`
`B=(x-1)(x^2 +x+1) -(x+1)(x^2 - x+1)`
`->B=(x^3 - 1^3) - (x^3 +1^3)`
`->B=x^3 - 1 - x^3 - 1`
`->B=-2`
Vậy `B=-2`
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`c,`
`C=(2x-y)(4x^2 + 2xy + y^2) + (y-3x)(y^2 + 3xy +9x^2)`
`->A=(2x)^3 - y^3 + y^3 - (3x)^3`
`->A=8x^3 - y^3 + y^3 - 27x^3`
`->A=-19x^3`
Vậy `A=-19x^3`
