Đáp án:
Giải thích các bước giải:
`x^2 - 5xy + 6y^2`
`=x^2 - 2xy - 3xy + 6y^2`
`=x(x - 2y) - 3y(x - 2y)`
`=(x - 2y)(x- 3y)`
1.
`x^4 y^4 + 4`
`=x^4y^4 + 4x^2y^2 + 4 - (2xy)^2`
`=(x^2y^2 + 2)^2 - (2xy)^2`
`=(x^2y^2 + 2 - 2xy)(x^2y^2 + 2 + 2xy)`
`3.`
`x^7 + x^2 + 1`
`=x^7 -x + x^2 + x + 1`
`=x(x^6 - 1) + (x^2 + x + 1`
`=x(x^3 - 1)(x^3 + 1) + (x^2 + x + 1)`
`=x(x - 1)(x^2 + x + 1)(x^3 + 1) + (x^2 + x + 1)`
`= (x^2 + x + 1)[x(x- 1)(x^3 + 1) + 1]`
`=(x^2−x+1)[(x^4−x)(x+1)−1]`
`=(x^2−x+1)(x^5+x^4−x^2−x−1)`
