Các câu hỏi tương tự
Cho A = \(\frac{9}{5^2}+\frac{9}{11^2}+\frac{9}{17^2}+.......+\frac{9}{409^2}\)
CMR A<\(\frac{1}{12}\)
Chứng minh :
1,C=\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{70}.C< \frac{3}{4}\)
2,D=\(\frac{1}{5^2}+\frac{1}{9^2}+...+\frac{1}{409^2}< \frac{1}{12}\)
3,E=\(\frac{5}{5.8.11}+\frac{5}{8.11.14}+...+\frac{5}{302.305.308}< \frac{1}{48}\)
Cho A = \(\frac{1}{5^2}+\frac{1}{11^2}+\frac{1}{17^2}+.......+\frac{1}{409^2}\)
CMR A<\(\frac{1}{12}\)
Cho S : = \(\frac{1}{5^2}+\frac{1}{9^2}+.....+\frac{1}{409^2}\) Chứng minh : S <\(\frac{1}{12}\)
Cho \(S=\frac{1}{5^2}+\frac{1}{9^2}+...+\frac{1}{409^2}.\)Chứng minh \(S<\frac{1}{12}\)
cho S = \(\frac{1}{5^2}+\frac{1}{9^2}+....+\frac{1}{409^2}\)chứng minh S <\(\frac{1}{12}\)
\(C=\frac{1}{5^2}+\frac{1}{9^2}+...+\frac{1}{409^2}.\)CHỨNG MINH \(C<\frac{1}{11}\)
\(S=\frac{1}{5^2}+\frac{1}{9^2}+...+\frac{1}{409^2}\)
chứng minh \(S
Bài 1 : Tính
Cho A =\(\frac{1}{31}+\frac{1}{32}+\frac{1}{33}+......+\frac{1}{60}>\frac{7}{12}\)
B = \(\frac{1}{3^2}+\frac{1}{3^2}+\frac{1}{5^2}+......+\frac{ }{50^{21}}\)
CMR B >\(\frac{1}{4}\)và B < \(\frac{4}{9}\)
C = \(\frac{1}{2}.\frac{3}{4}.\frac{5}{6}.\frac{7}{8}.......\frac{79}{80}< \frac{1}{9}\)