Đáp án:
Bài 1:
`a)6x³y²-8x^4y+2x²y²`
`b)x³-5x²+7x-2`
Bài 2:
`a)-5x-21`
`b)3`
Giải thích các bước giải:
Bài 1:
`a)2x²y.(3xy-4x²+y)`
`=2x²y.3xy-2x²y.4x²+2x²y.y`
`=6x³y²-8x^4y+2x²y²`
`b)(x-2)(x²-3x+1)`
`=x(x²-3x+1)-2(x²-3x+1)`
`=x³-3x²+x-2x²+6x-2`
`=x³-(3x²+2x²)+(x+6x)-2`
`=x³-5x²+7x-2`
Bài 2:
`a)3.(x²-7)-x.(3x+5)`
`=3x²-21-3x²-5x`
`=(3x²-3x²)-5x-21`
`=-5x-21`
`b)(3-2a).(a+1)+a(2a-1)`
`=3(a+1)-2a(a+1)+a(2a-1)`
`=3a+3-2a²-2a+2a²-a`
`=(-2a²+2a²)+(3a-2a-a)+3`
`=3`