Đáp án:
1. `x^2 + 2019x - 2020`
`= x^2 - x + 2020x - 2020`
`= x(x - 1) + 2020(x - 1)`
`= (x - 1)(x + 2020)`
2.`2020x^2 - x - 2021`
` = 2020x^2 - 2021x + 2020x - 2021`
`=x(2020x - 2021) + (2020x - 2021)`
`= (x + 1)(2020x - 2021)`
3. `3x^2 - 7x - 10`
`= 3x^2 + 3x - 10x - 10`
`= 3x(x + 1) - 10(x + 1)`
`= (x + 1)(3x - 10)`
4. `5x^2 + 17x - 22`
`= 5x^2 - 5x + 22x - 22`
`= 5x(x - 1) + 22(x - 1)`
`= (x - 1)(5x + 22)`
5. `100x^2 + 100x - 201` (Đề sai)
6. `x^3 - 15x^2 + 56x`
`= x^3 - 8x^2 - 7x^2 + 56x`
`= x^2 .(x - 8) - 7x(x - 8)`
`= x(x - 8)(x - 7)`
7.`x^3 + x^2 - 20x`
`= x^3 - 4x^2 + 5x^2 - 20x`
`= x^2 .(x - 4) + 5x.(x - 4)`
`= x(x - 4)(x + 5)`
8. `x^3 + 4x^2 - 21x`
`= x^3 - 3x^2 + 7x^2 - 21x`
`= x^2 .(x - 3) + 7x.(x - 3)`
`= x(x - 3)(x + 7)`
Giải thích các bước giải:
