a)-3/4 +3/7+(-1)/4+4/9+4/7 b)-7/9×4/11+(-7)/9.7/11+52/9 c) (21/31+2013/6039)-(44/53-10/31)-9/53

0 bình luận về “a)-3/4 +3/7+(-1)/4+4/9+4/7 b)-7/9×4/11+(-7)/9.7/11+52/9 c) (21/31+2013/6039)-(44/53-10/31)-9/53”

1. Đáp án:

   $\begin{array}{l}
   a)\dfrac{{ – 3}}{4} + \dfrac{3}{7} + \dfrac{{ – 1}}{4} + \dfrac{4}{9} + \dfrac{4}{7}\\
    = \dfrac{{ – 3}}{4} + \dfrac{{ – 1}}{4} + \dfrac{3}{7} + \dfrac{4}{7} + \dfrac{4}{9}\\
    = \dfrac{{ – 4}}{4} + \dfrac{7}{7} + \dfrac{4}{9}\\
    =  – 1 + 1 + \dfrac{4}{9}\\
    = \dfrac{4}{9}\\
   b)\dfrac{{ – 7}}{9}.\dfrac{4}{{11}} + \dfrac{{ – 7}}{9}.\dfrac{7}{{11}} + \dfrac{{52}}{9}\\
    =  – \dfrac{7}{9}.\left( {\dfrac{4}{{11}} + \dfrac{7}{{11}}} \right) + \dfrac{{52}}{9}\\
    =  – \dfrac{7}{9}.\dfrac{{11}}{{11}} + \dfrac{{52}}{9}\\
    =  – \dfrac{7}{9} + \dfrac{{52}}{9}\\
    = \dfrac{{45}}{9}\\
    = 5\\
   c)\left( {\dfrac{{21}}{{31}} + \dfrac{{2013}}{{6039}}} \right) – \left( {\dfrac{{44}}{{53}} – \dfrac{{10}}{{31}}} \right) – \dfrac{9}{{53}}\\
    = \dfrac{{21}}{{31}} + \dfrac{1}{3} – \dfrac{{44}}{{53}} + \dfrac{{10}}{{31}} – \dfrac{9}{{53}}\\
    = \left( {\dfrac{{21}}{{31}} + \dfrac{{10}}{{31}}} \right) + \dfrac{1}{3} + \left( { – \dfrac{{44}}{{53}} – \dfrac{9}{{53}}} \right)\\
    = \dfrac{{31}}{{31}} + \dfrac{1}{3} – \dfrac{{53}}{{53}}\\
    = 1 + \dfrac{1}{3} – 1\\
    = \dfrac{1}{3}
   \end{array}$

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