Đáp án+Giải thích các bước giải:
`a)x(x²-5x+2)-(x-3)(x²-2)`
`= x³-5x²+2x-(x³-2x-3x²+6)`
`= x³-5x²+2x-x³+2x+3x²-6`
`= -2x²+4x-6`
`b) 4x(x²-x-1)-(x²-2)(x+3)`
`= 4x³-4x²-4x-(x³+3x²-2x-6)`
`= 4x³-4x²-4x-x³-3x²+2x+6`
`= 3x³-7x²-2x+6`
`c) (x-5)(x+7)-7x(x+3)`
`= x²+2x-35-7x²-21x`
`= -6x²-19x-35`
`d) x(x²-x-2)-(x+5)(x-1)`
`= x³-x²-2x-(x²+4x-5)`
`= x³-x²-2x-x²-4x+5`
`= x³-2x²-6x+5`