Bài 1 . Tính : a ) $\left(2x-1\right)\left(3x+2\right)\left(3-x\right)$ b ) $\left(x-2y\right)^2$ c ) $\left(2x^2+3\right)^2$ d ) $\left(x-2\right)\left(x^2+2x+4\right)$ e ) $\left(2x-1\right)^3$

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

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

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

`=18x^2-6x^3+3x-x^2-6+2x`

`=17x^2-6x^3+5x-6`

`=-6x^3+17x^2+5x-6`

`b)` `(x-2y)^2`

`=x^2-2x.2y+(2y)^2`

`=x^2-4xy+4y^2`

`c)` `(2x^2+3)^2`

`=(2x^2)^2+2.2x^2.3+3^2`

`=4x^4+12x^2+9`

`d)` `(x-2)(x^2+2x+4)`

`=x^3-2^3`

`=x^3-8`

`e)` `(2x-1)^3`

`=(2x)^3-3.(2x)^2.1+3.2x.1^2-1^3`

`=8x^3-3.4x^2.1+3.2x.1-1`

`=8x^3-12x^2+6x-1`