Tính a) \(A=\frac{1}{2.9}+\frac{1}{9.7}+\frac{1}{7.19}+...+\frac{1}{252.509}\) b) \(B=\frac{1}{10.9}+\frac{1}{18.13}+\frac{1}{26.17}+...+\frac{1}{802.405}\)Tìm x là số tự nhiên:\(\frac{x}{2008}-\frac{1}{10}-\frac{1}{15}-\frac{1}{21}-...-\frac{1}{120}=\frac{5}{8}\)\(A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}\)\(CMR:\frac{16}{81}< A< \frac{16}{80}\) ...
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Tính
a) \(A=\frac{1}{2.9}+\frac{1}{9.7}+\frac{1}{7.19}+...+\frac{1}{252.509}\)
b) \(B=\frac{1}{10.9}+\frac{1}{18.13}+\frac{1}{26.17}+...+\frac{1}{802.405}\)
Tìm x là số tự nhiên:
\(\frac{x}{2008}-\frac{1}{10}-\frac{1}{15}-\frac{1}{21}-...-\frac{1}{120}=\frac{5}{8}\)
\(A=\frac{4}{15.19}+\frac{4}{19.23}+...+\frac{4}{399.403}\)\(CMR:\frac{16}{81}< A< \frac{16}{80}\)
