7/-25+-18/25+4/23+5/7+19/23 7/19×8/11+7/19×3/11+12/19 82/7-(34/9+42/7) (2/5-3/4)-2/5 Câu 82/7 là hỗn số nhé

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1. Đáp án:

   $\begin{array}{l}
   \dfrac{7}{{ – 25}} + \dfrac{{ – 18}}{{25}} + \dfrac{4}{{23}} + \dfrac{5}{7} + \dfrac{{19}}{{23}}\\
    = \dfrac{{ – 7}}{{25}} + \dfrac{{ – 18}}{{25}} + \dfrac{4}{{23}} + \dfrac{{19}}{{23}} + \dfrac{5}{7}\\
    = \dfrac{{ – 25}}{{25}} + \dfrac{{23}}{{23}} + \dfrac{5}{7}\\
    =  – 1 + 1 + \dfrac{5}{7}\\
    = \dfrac{5}{7}\\
   \dfrac{7}{{19}}.\dfrac{8}{{11}} + \dfrac{7}{{19}}.\dfrac{3}{{11}} + \dfrac{{12}}{{19}}\\
    = \dfrac{7}{{19}}.\left( {\dfrac{8}{{11}} + \dfrac{3}{{11}}} \right) + \dfrac{{12}}{{19}}\\
    = \dfrac{7}{{19}}.1 + \dfrac{{12}}{{19}}\\
    = \dfrac{{19}}{{19}} = 1\\
   8\dfrac{2}{7} – \left( {3\dfrac{4}{9} + 4\dfrac{2}{7}} \right)\\
    = 8\dfrac{2}{7} – 4\dfrac{2}{7} – 3\dfrac{4}{9}\\
    = 4\dfrac{2}{7} – 3\dfrac{4}{9}\\
    = \dfrac{{30}}{7} – \dfrac{{31}}{9}\\
    = \dfrac{{53}}{{63}}\\
   \left( {\dfrac{2}{5} – \dfrac{3}{4}} \right) – \dfrac{2}{5}\\
    = \dfrac{2}{5} – \dfrac{3}{4} – \dfrac{2}{5}\\
    =  – \dfrac{3}{4}
   \end{array}$

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2. Đáp án:

   7−25+−1825+423+57+1923=−725+−1825+423+1923+57=−2525+2323+57=−1+1+57=57719.811+719.311+1219=719.(811+311)+1219=719.1+1219=1919=1827−(349+427)=827−427−349=427−349=307−319=5363(25−34)−25=25−34−25=−34

   Giải thích các bước giải:

    

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