[toán 6] tính nhanh nè!

C

conbaodn

1[tex] \frac{8}{9} - \frac{1}{72} - \frac{1}{56} - \frac{1}{42} - \frac{1}{30} - \frac{1}{20} - \frac{1}{12} - \frac{1}{6} - \frac{1}{2})[/tex]
[tex] \Rightarrow \frac{8}{9} - (\frac{1}{2} + \frac{1}{6} + \frac{1}{12} + \frac{1}{20} + \frac{1}{30} + \frac{1}{42} + \frac{1}{56} + \frac{1}{72})[/tex]
[tex] \Rightarrow \frac{8}{9} - (\frac{1}{1.2} + \frac{1}{2.3} + \frac{1}{3.4} + \frac{1}{4.5} + \frac{1}{5.6} + \frac{1}{6.7} + \frac{1}{7.8})[/tex]
[tex] \Rightarrow \frac{8}{9} - (1-\frac{1}{2} + \frac{1}{2} - \frac{1}{3} +...+ \frac{1}{7} - \frac{1}{8} +\frac{1}{8} - \frac{1}{9})[/tex]
[tex] \Rightarrow \frac{8}{9} - (1 - \frac{1}{9} =0[/tex]
Nhớ Thanks Mình Nhé
 
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