Phân tích đa thức thành nhân tử ạ

khai bút đầu nămm >.<

`bb17.`

`2x^2 - 5x - 3`

`= 2x^2 + x - 6x - 3`

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

`= x(2x + 1) - 3(2x + 1)`

`= (2x + 1)(x - 3)`

`bb18.`

`3x^2 - 5x - 2`

`= 3x^2 + x - 6x - 2`

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

`= x(3x + 1) - 2(3x + 1)`

`= (3x + 1)(x - 2)`

`bb19.`

`x^2 + 2x - 3`

`= x^2 + 3x - x - 3`

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

`= x(x + 3) - (x + 3)`

`= (x + 3)(x - 1)`

`bb20.`

`x^3 - 7x + 6`

`= x^3 - x^2 + x^2 - x - 6x + 6`

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

`= x^2(x - 1) + x(x - 1) - 6(x - 1)`

`= (x - 1)(x^2 + x - 6)`

`= (x - 1)(x^2 + 3x - 2x - 6)`

`= (x - 1)[x(x + 3) - 2(x + 3)]`

`= (x - 1)(x + 3)(x - 2)`

`bb21.`

`x^3 + 5x^2 + 8x + 4`

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

`= (x^3 + x^2) + (4x^2 + 4x) + (4x + 4)`

`= x^2(x + 1) + 4x(x + 1) + 4(x + 1)`

`= (x + 1)(x^2 + 4x + 4)`

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

`---`

`#mênhh`