Đáp án:
`A=-6x³-2x²+12x+4`
`B=3x³+12xy²-6x²y-24y³`
`C=-12x²y+23xy-10y`
`D=-6x³y²-12xy²-18x²y-36y`
Giải thích các bước giải:
`A=(1+3x)(4-2x²)`
`=1(4-2x²)+3x(4-2x²)`
`=4-2x²+12x-6x³`
`=-6x³-2x²+12x+4`
`B=(3x-6y)(x²+4y²)`
`=3x(x²+4y²)-6y(x²+4y²)`
`=3x³+12xy²-6x²y-24y³`
`C=(-4x+5)(3xy-2y)`
`=-4x(3xy-2y)+5(3xy-2y)`
`=-12x²y+8xy+15xy-10y`
`=-12x²y+23xy-10y`
`D=(3xy+9)(-2x²y-4y)`
`=3xy(-2x²y-4y)+9(-2x²y-4y)`
`=-6x³y²-12xy²-18x²y-36y`