CHO
\(\frac{1}{M}=\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}+...+\frac{1}{1+2+3+...+59}\)
Chứng minh rằng M>\(\frac{2}{3}\)
Cho M =\(\frac{1}{1+2+3}\)+\(\frac{1}{1+2+3+4}\)+..............................+\(\frac{1}{1+2+3+..........+59}\)
Chứng minh M<\(\frac{2}{3}\)
\(ChoM+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+....+\frac{1}{1+2+3+4+...+59}.\)
Chứng minh rằng \(M< \frac{2}{3}\)
M=\(\frac{1}{1+2+3}\)+\(\frac{1}{1+2+3+4}\)+..............+\(\frac{1}{1+2+3+...+59}\)
chứng minh M<\(\frac{2}{3}\)
Chứng minh
M=\(\frac{1}{1+2+3}\)+\(\frac{1}{1+2+3+4}\)+\(\frac{1}{1+2+3+4+5}\)+.....+\(\frac{1}{1+2+3+....+59}\)<\(\frac{2}{3}\)
Cho M = \(\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+......+\frac{1}{1+2+3+.....+89}\)
Chứng minh M\(< \frac{2}{3}\)
\(Cho:M=\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...+\frac{1}{1+2+3+...+59}\)
Chứng mính: \(M<\frac{2}{3}\)
Cho \(M = (1+\frac{1}{2}+\frac{1}{3}+...++\frac{1}{2018}).2 .3 .4. ... .2018\)
Chứng minh : M chia hết cho 2019
