a)(3x-1)(2x+3)-(x-5)(6x-1)-38x b)(x-2y)(x^2+2xy+4y^2)-x^3+5+8y^3) c)(5x-2)(x+1)-(x-3)(5x+1)-17(x-2)

Đáp án + Giải thích các bước giải:

 `a)` `(3x-1)(2x+3) - (x-5)(6x-1) -38x`

`= 6x^2 - 2x + 9x - 3 - (6x^2 - 30x - x + 5 ) - 38x`

`= 6x^2 - 31x - 3 - 6x^2 + 31x - 5`

`= -8`

`b)` `(x-2y)(x^2 + 2xy + 4y^2 ) - x^3 + 5 + 8y^3`

`= (x-2y)[x^2 + x.2y + (2y)^2] - x^3 + 5 + 8y^3`

`= x^3 - (2y)^3 - x^3 + 5 + 8y^3 = 5`

`c)` `(5x-2)(x+1) - (x-3)(5x-1) - 17(x-2)`

`= 5x^2 - 2x + 5x - 3 - ( 5x^2 - 15x - x + 3 ) - 17x + 34`

`= 5x^2 -14x + 31 - 5x^2 + 16x - 3`

`= 2x + 28`