giúp vs cứu em bài 1

a) `2x . (x-3) + 3x^2 - 4x -1`

`= 2x . x - 2x . 3 + 3x^2 - 4x - 1`

`= 2x^2 - 6x + 3x^2 - 4x - 1`

`= (2x^2 + 3x^2) - (6x+4x) - 1`

`= 5x^2 - 10x - 1`

b) `B = (-2)/3 x^2 - 5x . (1/3x + 1) - x + 2 + 4x`

`= (-2)/3 x^2 - 5/3x^2 - 5x - x + 2 + 4x`

`= - (2/3x^2 + 5/3x^2) - (5x + x - 4x) + 2`

`= -7/3x^2 - 2x + 2`

c) `C = 3x^2 - (2x - 5) - x . (3x+2) - x`

`= 3x^2 - 2x + 5 - x . 3x - x . 2 - x`

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

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

`= -5x + 5`