a)81x^4(z^2-y^2)-z^2+y^2\\\\\\B)x^2(y-z)+y^2(z-x)+z^2(x-y)

Đáp án + Giải thích các bước giải:

`a)81x^4(z^2-y^2)-z^2+y^2`

`=81x^4(z^2-y^2)-(z^2-y^2)`

`=(z^2-y^2)(81x^4 - 1)`

`=(z - y)(z + y)(9x^2 - 1)(9x^2 + 1)`

`=(z - y)(z + y)(3x - 1)(3x + 1)(9x^2 + 1)`

`b)x^2(y-z)+y^2(z-x)+z^2(x-y)`

`=x^2(y - z) + y^2z - y^2x + z^2x - z^2y`

`=x^2(y - z) + y^2z - z^2y - y^2x + z^2x`

`=x^2(y - z) + yz( y -z) - x (y^2- z^2)`

`=x^2(y - z) + yz( y -z) - x (y-z)(y + z)`

`=(y - z)(x^2 + yz - xy - xz) `

`=(y - z)(x^2 - xy + yz  - xz)`

`=( y - z)[x(x - y) - z( x - y)]`

`=(y - z)(x-  y)(x - z)`