Giải thích các bước giải:
`Câu` `1:`
`2x.(x -4)² -(x +5).(x -2).(x +2) +(2x +5)² -(x -1)²`
`= 2x.(x -4)² -(x +5).(x² -4) +(2x +5 -x +1).(2x +5 +x -1)`
`= 2x.(x -4)² -(x +5).(x² -4) +(x +6).(3x +4)`
`= 2x.(x² -8x +16) -(x³ -4x +5x² -20) +(3x² +4x +18x +24)`
`= 2x³ -16x² +32x -x³ +4x -5x² +20 +3x² +4x +18x +24`
`= x³ -18x² +58x +44`
`Câu` `2:`
`(x +5)²- 4x(2x +3)² -(2x -1)(x +3)(x -3)`
`= x² +10x +25 -4x.(4x² +12x +9) -(2x -1).(x² -9)`
`= x² +10x +25 -16x³ -48x² -36x -2x³ +18x +x² -9`
`= -46x² -18x³ -8x +16`
`Câu` `3:`
`-2x(3x -2)(3x +2) +5(x +2)² -(x -1)(2x -1)(-2x +1)`
`= -2x.(9x² -4) +5.(x² +4x +4) +(x -1).(2x -1)²`
`= -18x³ +8x +5x² +20x +20 +(x -1).(4x² -4x +1)`
`= -18x³ +5x² +28x +20 +4x³ -4x² +x -4x² +4x -1`
`= -14x³ -3x² +33x +19`
