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\(A=\frac{14}{15}.\frac{20}{21}.\frac{27}{28}....\frac{209}{210}=\frac{28}{30}.\frac{40}{42}.\frac{54}{56}....\frac{418}{420}=\frac{4.7}{5.6}.\frac{5.8}{6.7}.\frac{6.9}{7.8}....\frac{19.22}{20.21}\)
\(=\frac{4.5.6...19}{5.6.7...20}.\frac{7.8.9...22}{6.7.8...21}=\frac{4}{20}.\frac{22}{6}=\frac{11}{5}\)
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=14\15.20\21....209\210
=14.2\15.2.20.2\21.2....209.2\210.2
=4.7\5.6.5.8\6.7.....19.20\20.21
=4.5.6....19\5.6.7...20.7.8.9....22\6.7.8.....21
=4\20.22\6
=1\5-11\3
=11\15
k cho mik nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Rightarrow A=\frac{14}{15}.\frac{20}{21}.\frac{41}{42}.....\frac{209}{210}\)
\(=\frac{4.7}{5.6}.\frac{5.8}{6.7}.\frac{6.9}{7.8}.....\frac{19.22}{20.21}\)
\(=\frac{22}{6}=\frac{11}{3}\)
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xin loi nhung ma minh cung dang khong giai duoc cau nay, minh mong cac ban tren Online Math giup minh nhe