Phân tích đa thức thành nhân tử Cảm ơn mng nhiều lun:(

~ Bạn tham khảo ~

`7) x^4 + 3x^3 + x^2 - 12x - 20`

` = x^4 + 2x^3 + x^3 + 2x^2 - x^2 - 2x - 10x - 20`

` = x^3(x + 2) + x^2(x + 2) - x(x + 2) - 10(x + 2)`

` = (x + 2)(x^3 + x^2 - x - 10)`

` = (x + 2)(x^3 - 2x^2 + 3x^2 - 6x + 5x - 10)`

` = (x + 2)[ x^2(x - 2) + 3x(x - 2) + 5(x - 2)]`

` = (x + 2)(x - 2)(x^2 + 3x + 5)`

`8) 2x^4 + 5x^3 + 13x^2 + 25x + 15`

`= 2x^4 + 3x^3 + 2x^3 + 3x^2 + 10x^2 + 15x + 10x + 15`

` = x^3(2x + 3) + x^2(2x + 3) + 5x(2x + 3) + 5(2x + 3)`

` = (2x +3)(x^3 + x^2 + 5x + 5)`

` = (2x + 3)[ x^2(x + 1) + 5(x + 1)]`

` = (2x + 3)(x + 1)(x^2 + 5)`