Đáp án:
`1)2(x−2)(x+4)`
`=(2x−4).(x+4)`
`=2x^2+8x−4x−16`
`=2x^2+4x−16`
`2)5.(x−2)(x−3)`
`=(5x−10)(x−3)`
`=5x^2−15x−10x+30`
`=5x^2−25x+30`
`3)−3(2x^2+1)(x−3)`
`=(−6x^2−3)(x−3)`
`=−6x^3+18x^2−3x+9`
`4)−5x(x−1)(x^2−2x)`
`=(−5x^2+5x)(x^2−2x)`
`=−5x^4+10x^3+5x^3−10x^2`
`=−5x^4+15x^3−10x^2`
`5)2x^3 (4−2x)(x+1)`
`=(8x^3−4x^4)(x+1)`
`=8x^4+8x^3−4x^5−4x^4`
`=−4x^5+4x^4+8x^3`
`6)3x^2(2x−3)(2−x^2)`
`=(6x^3−9x^2)(2−x^2)`
`=12x^3−6x^5−18x^2+9x^4`
`7)(x−1)(x−2)(x−3)`
`=(x^2−3x+2)(x−3)`
`=x^3−3x^2−3x^2+9x+2x−6`
`=x^3−6x^2+11x−6`
`8, (x + 2)(2x - 1)(3x - 2)`
`= (2x^2 - x + 4x - 2)(3x - 2)`
`= 6x^3 - 4x^2 - 3x^2 + 2x + 12x^2 - 8x- 6x + 4`
`= 6x^3 + (-4x^2 - 3x^2 + 12x^2) + (2x - 8x - 6x) + 4`
`= 6x^3 + 5x^2 - 12x + 4`
`9, (3x - 2)(x - 4)(3x + 1)`
`= (3x^2 - 12x - 2x + 8)(3x + 1)`
`= 9x^3 + 3x^2 - 36x^2 - 12x - 6x^2 - 2x + 24x + 8`
`= 9x^3 + (3x^2 - 36x^2 - 6x^2) + (-12x - 2x + 24x) + 8`
`= 9x^3 - 39x^2 + 10x + 8`
