Tính: \({8 \over 9}:\left( {{3 \over 5} - {2 \over 7}} \right) - {8 \over 9}:\left( {{6 \over 7} - {4 \over 5}} \right)\)
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Lời giải:
Báo sai\(\begin{array}{l}\frac{8}{9}:\left( {\frac{3}{5} - \frac{2}{7}} \right) - \frac{8}{9}:\left( {\frac{6}{7} - \frac{4}{5}} \right)\\ = \frac{8}{9}:\left( {\frac{{21}}{{35}} - \frac{{10}}{{35}}} \right) - \frac{8}{9}:\left( {\frac{{30}}{{35}} - \frac{{28}}{{35}}} \right)\\ = \frac{8}{9}:\frac{{11}}{{35}} - \frac{8}{9}:\frac{2}{{35}}\\ = \frac{8}{9}.\frac{{35}}{{11}} - \frac{8}{9}.\frac{{35}}{2}\\ = \frac{8}{9}.\left( {\frac{{35}}{{11}} + \frac{{35}}{2}} \right)\\ = \frac{8}{9}.\left( {\frac{{70}}{{22}} - \frac{{385}}{{22}}} \right)\\ = \frac{8}{9}.\frac{{ - 315}}{{22}}\\ = \frac{{2.4}}{9}.\frac{{ - 35.9}}{{2.11}}\\ = \frac{{ - 140}}{{11}}\end{array}\)