`1)(x+1)(x²-x+1)`
`=(x+1)(x²-x.1+1²)`
`=x³+1³`
`=x³+1`
Áp dụng HĐT:`A³+B³=(A+B)(A²-AB+B²)`
`2)(x-3)(x²+3x+9)`
`=(x-3)(x²+x.3+3²)`
`=x³-3³`
`=x³-27`
Áp dụng HĐT:`A³-B³=(A-B)(A²+AB+B²)`
`3)(x-2)(x²+2x+4)`
`=(x-2)(x²+x.2+2²)`
`=x³-2³`
`=x³-8`
Áp dụng HĐT:`A³-B³=(A-B)(A²+AB+B²)`
`4)(x+4)(x²-4x+16)`
`=(x+4)(x²-x.4+4²)`
`=x³+4³`
`=x³+64`
Áp dụng HĐT:`A³+B³=(A+B)(A²-AB+B²)`
`5)(x-3y)(x²+3xy+9y²)`
`=(x-3y)[x²+x.3y+(3y)²]`
`=x³-(3y)³`
`=x³-27y³`
Áp dụng HĐT:`A³-B³=(A-B)(A²+AB+B²)`
`6)(x²-1/3)(x^4+1/3x²+1/9)`
`=(x²-1/3)[(x^2)^2+x². 1/3+(1/3)^2]`
`=(x^2)^3-(1/3)^3`
`=x^6-1/27`
Áp dụng HĐT:`A³-B³=(A-B)(A²+AB+B²)`
`7)(1/3x+2y)(1/9x²-2/3xy+4y²)`
`=(1/3x+2y)[(1/3x)^2-1/3x.2y+(2y)²]`
`=(1/3x)^3+(2y)^3`
`=1/27x³+8y³`
Áp dụng HĐT:`A³+B³=(A+B)(A²-AB+B²)`
