Chứng minh rằng:
a) \(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}<\frac{1}{4}\)
b)\(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}>\frac{1}{5}\)
Chứng minh rằng: \(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}>\frac{1}{5}.\)
Mình cần gấp lắm! Help me!
Chứng minh : \(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{^{2007^2}}<\frac{50}{251}\)
Chứng minh rằng:
\(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}<\frac{1}{4}\)
Chứng minh: \(\frac{1}{5^2}+\frac{1}{6^2}+...+\frac{1}{2007^2}>\frac{1}{5}\)
Chứng minh rằng: \(\frac{1}{5}< \frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}< \frac{1}{4}\)
\(\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+...+\frac{1}{2007^2}>\frac{1}{5}\)
\(Chứngminh\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+....+\frac{1}{2007^2}>\frac{1}{5}\)
chứng minh rằng:\(1+\frac{1}{2}+\frac{1}{2}+\frac{1}{12}+\left(\frac{1}{5}+\frac{1}{6}+\frac{1}{7}+\frac{1}{8}\right)+...+\frac{1}{257}+\frac{1}{258}+....+\frac{1}{455}>1+\frac{1}{2}+\frac{1}{2}+\left(\frac{1}{5}+\frac{1}{6}+\frac{1}{7}+\frac{1}{8}\right)+.....+\left(\frac{1}{257}+\frac{1}{258}+...+\frac{1}{512}\right)\)
