Question

BT3: Rút gọn biểu thức

d, (x-2)^3-x(x+1)(x-1)+6x(x-2)

Answer 1

=x^3-6x^2+12x-8-x^3+x+6x^2-12x

=x-8

Answer 2

`@` `\text {Ans}`

`\downarrow`

`d,`

\((x-2)^3-x(x+1)(x-1)+6x(x-2)\)

`= x^3 - 6x^2 + 12x - 8 - [x(x^2 - 1)] + 6x^2 - 12x`

`= x^3 - 6x^2 + 12x - 8 - x^3 + x + 6x^2 - 12x`

`= (x^3 - x^3) + (-6x^2 + 6x^2) + (12x - 12x) -8`

`= x - 8`