Đáp án:
`a)P=9x³-3x²+x+2`
`b)Q=-2x²y+2y²+2y³`
Giải thích các bước giải:
`a)P=(2x-1)4x²+2x+1+(x+1)x²-x+1`
`=8x³-4x²+2x+1+x³+x²-x+1`
`=(8x³+x³)+(-4x²+x²)+(2x-x)+(1+1)`
`=9x³-3x²+x+2`
`b)Q=(x-y)x²+xy+y²-(x+y)x²-xy+y²+2y³`
`=x³-x²y+xy+y²-x³-x²y-xy+y²+2y³`
`=(x³-x³)+(-x²y-x²y)+(xy-xy)+(y²+y²)+2y³`
`=-2x²y+2y²+2y³`