15.[-1/5]^2+1/5-2.[-1/2]^3-1/2

Đáp án:

 `15.(-\frac{1}{5})^{2}+\frac{1}{5}-2.(-\frac{1}{2})^{3}-\frac{1}{2}`

`=15.(\frac{1}{5})^{2}+\frac{1}{5}-2.(-1).(\frac{1}{2})^{3}-\frac{1}{2}`

`=\frac{1}{5}.(15.\frac{1}{5}+1)+2.(\frac{1}{2})^{3}-\frac{1}{2}`

`=\frac{1}{5}.(\frac{15}{5}+1)+\frac{1}{2}.(2.(\frac{1}{2})^{2}-1)`

`=\frac{1}{5}.(3+1)+\frac{1}{2}.(2.\frac{1}{4}-1)`

`=\frac{1}{5}.4+\frac{1}{2}.\frac{-1}{2}`

`=\frac{4}{5}+\frac{-1}{4}`

`=\frac{16}{20}-\frac{5}{20}`

`=\frac{11}{20}`