giúp mình với ạ !!!!

Đáp án:

 `(\frac{x}{2}-2y)^{3}`

`=(\frac{x}{2})^{3}-3.(\frac{x}{2})^{2}.2y+3.\frac{x}{2}.(2y)^{2}-(2y)^{3}`

`=\frac{x^{3}}{8}-3.\frac{x^{2}}{4}.2y+3.\frac{x}{2}.4y^{2}-8y^{3}`

`=\frac{x^{3}}{8}-\frac{3x^{2}.2y}{4}+\frac{3.x.4y^{2}}{2}-8y^{3}`

`=\frac{x^{3}}{8}-\frac{3x^{2}y}{2}+6xy^{2}-8y^{3}`