13.

`(-4)/13. 5/17+(-12)/13. 4/17 + 4/13`

`=(-4)/13. 5/17+(-12)/17. 4/13 + 4/13`

`=4/13.((-5)/17+(-12)/17+1)`

`=4/13.(-1+1)`

`=4/13. 0`

`=0`

14. 

`(-13. 2/5+ (-2)/9:2 1/2+2/5. 11/9):2 1/2`

`=(-13. 2/5+ (-2)/9:5/2+2/5. 11/9):2 1/2`

`=(-13. 2/5+ (-2)/9. 2/5+2/5. 11/9):2 1/2`

`=2/5.(-13+ (-2)/9+ 11/9). 2/5`

`=2/5.(-12). 2/5`

`=-48/25`

15. 

`(-3/4+2/7). 3/2 +((-1)/4+5/7). 3/2`

`=(-3/4+2/7+(-1)/4+5/7). 3/2`

`=((-4)/4+7/7). 3/2`

`=(-1+1). 3/2`

`=0. 3/2`

`=0`

16.

`(5/4-2/5). 2015/2016 +(3/4-3/5). 2015/2016`

`=(5/4-2/5+3/4-3/5). 2015/2016 `

`=(5/4-2/5+3/4-3/5). 2015/2016 `

`=(8/4-5/5). 2015/2016 `

`=(2-1). 2015/2016 `

`=1. 2015/2016 `

`=2015/2016 `

Đáp án:

\(13)\ 0\\ 14)\ \dfrac{-48}{25}\\ 15)\ 0\\ 16)\ \dfrac{2015}{2016}\)

Giải thích các bước giải:

\(13)\ \dfrac{-4}{13}.\dfrac{5}{17}+\dfrac{-12}{13}.\dfrac{4}{17}+\dfrac{4}{13}\\ =\dfrac{4}{13}.\dfrac{-5}{17}+\dfrac{4}{13}.\dfrac{-12}{17}+\dfrac{4}{13}\\ =\dfrac{4}{13}.\bigg(\dfrac{-5}{17}-\dfrac{12}{17}+1\bigg)\\ =\dfrac{4}{13}.0\\ =0\\ 14)\ \bigg(-13.\dfrac{2}{5}+\dfrac{-2}{9}:2\dfrac{1}{2}+\dfrac{2}{5}.\dfrac{11}{9}\bigg):2\dfrac{1}{2}\\ =\bigg(-13.\dfrac{2}{5}+\dfrac{-2}{9}.\dfrac{2}{5}+\dfrac{11}{9}.\dfrac{2}{5}\bigg).\dfrac{2}{5}\\ =\bigg(-13-\dfrac{2}{9}+\dfrac{11}{9}\bigg).\dfrac{2}{5}.\dfrac{2}{5}\\ =-12.\dfrac{4}{25}\\ =\dfrac{-48}{25}\\ 15)\ \bigg(\dfrac{-3}{4}+\dfrac{2}{7}\bigg).\dfrac{3}{2}+\bigg(\dfrac{-1}{4}+\dfrac{5}{7}\bigg).\dfrac{3}{2}\\ =\dfrac{3}{2}.\bigg(\dfrac{-3}{4}+\dfrac{2}{7}+\dfrac{-1}{4}+\dfrac{5}{7}\bigg)\\ =\dfrac{3}{2}.\bigg[\bigg(\dfrac{-3}{4}-\dfrac{1}{4}\bigg)+\bigg(\dfrac{2}{7}+\dfrac{5}{7}\bigg)\bigg]\\ =\dfrac{3}{2}.(-1+1)\\ =\dfrac{3}{2}.0=0\\ 16)\ \bigg(\dfrac{5}{4}-\dfrac{2}{5}\bigg).\dfrac{2015}{2016}+\bigg(\dfrac{3}{4}-\dfrac{3}{5}\bigg).\dfrac{2015}{2016}\\ =\dfrac{2015}{2016}.\bigg(\dfrac{5}{4}-\dfrac{2}{5}+\dfrac{3}{4}-\dfrac{3}{5}\bigg)\\ =\dfrac{2015}{2016}.\bigg[\bigg(\dfrac{5}{4}+\dfrac{3}{4}\bigg)+\bigg(\dfrac{-2}{5}-\dfrac{3}{5}\bigg)\bigg]\\ =\dfrac{2015}{2016}.(2-1)\\ =\dfrac{2015}{2016}.1=\dfrac{2015}{2016}\)

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