Thực hiện các phép tính: \(C = \dfrac{{ - 2018}}{{2019}}.\dfrac{2}{7} - \dfrac{{2018}}{{2019}}.\dfrac{5}{7} + 1\dfrac{{2018}}{{2019}}\)
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Lời giải:
Báo sai\(C = \dfrac{{ - 2018}}{{2019}}.\dfrac{2}{7} - \dfrac{{2018}}{{2019}}.\dfrac{5}{7} + 1\dfrac{{2018}}{{2019}}\)
\( = \dfrac{{ - 2018}}{{2019}}.\dfrac{2}{7} + \dfrac{{ - 2018}}{{2019}}.\dfrac{5}{7}\)\( + \left( {1 + \dfrac{{2018}}{{2019}}} \right)\)
\(\begin{array}{l} = \dfrac{{ - 2018}}{{2019}}.\left( {\dfrac{2}{7} + \dfrac{5}{7}} \right) + 1 + \dfrac{{2018}}{{2019}}\\ = \dfrac{{ - 2018}}{{2019}}.\dfrac{7}{7} + 1 + \dfrac{{2018}}{{2019}}\\ = \dfrac{{ - 2018}}{{2019}} + 1 + \dfrac{{2018}}{{2019}}\\ = \dfrac{{ - 2018}}{{2019}} + \dfrac{{2018}}{{2019}} + 1\\ = 0 + 1 = 1\end{array}\)