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Giải thích
\(\frac{5}{9}\,\, \times \,\,\frac{8}{{15}}\,\, + \,\,\frac{5}{9}\,\, \times \,\,\frac{7}{{15}}\,\, - \,\,\frac{5}{9}\) \( = \frac{5}{9}\, \times \,\left( {\frac{8}{{15}}\,\, + \,\frac{7}{{15}}\,\, - \,1} \right)\) \( = \frac{5}{9}\, \times \,\left( {\frac{8}{{15}}\,\, + \,\,\frac{7}{{15}}\,\, - \,\frac{{15}}{{15}}} \right)\) \( = \frac{5}{9} \times \,\,\frac{{8 + 7 - 15}}{{15}}\) \( = \frac{5}{9}\,\, \times 0\) = 0 | \(\frac{4}{7}\,\, + \,\,\frac{4}{9}\,\, + \,\,\frac{3}{7}\,\, + \,\,\frac{5}{9}\,\, - \,\,1\) \( = \left( {\frac{4}{7}\,\, + \,\,\frac{3}{7}\,\,} \right) + \,\,\left( {\frac{4}{9}\,\, + \,\,\frac{5}{9}} \right)\,\, - \,\,1\) \( = \frac{7}{7} + \,\,\frac{9}{9} - \,\,1\) = 1 + 1 – 1 = 1 |