Đáp án + Giải thích các bước giải:
`a) x^4y^4-z^4`
`= (x²y²)²-(z²)²`
`=( x²y²-z²)(x²y²+z²)`
`b) (x+y+z)²-4z²`
`= (x+y+z)²-(2z)²`
`= (x+y+z-2z)(x+y+z+2z)`
`= (x+y-z)(x+y+3z)`
`c) (-1)/9 x² + 1/3xy -1/4y²`
`= -(1/9 x²-1/3xy+1/4 y²)`
`= -(1/3 x -1/2 y)²`
`d) x³y³ +125`
`= (xy)³+5³`
`= (xy+5)(x²y²-5xy+25)`