Cho 1/M=1/(1+2+3) + 1/(1+2+3+4) +.....+ 1/(1+2+3+4+...+59)
Chứng minh rằng M>2/3
Cho M=(1/1+2+3)+(1/1+2+3+4)+...+(1/1+2+3+...+59) . Chứng minh M<2/3
1. Chứng minh: \(\left(2^1+2^2+2^3+2^4+...+2^{59}+2^{60}\right):3\)
2. Chứng minh: \(M=3^{n+3}+3^{n+1}+2^{n+3}+2^{n+2}⋮6\)
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<2/3
Chứng minh
M=\(\frac{1}{1+2+3}\)+\(\frac{1}{1+2+3+4}\)+\(\frac{1}{1+2+3+4+5}\)+.....+\(\frac{1}{1+2+3+....+59}\)<\(\frac{2}{3}\)
\(ChoM+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+....+\frac{1}{1+2+3+4+...+59}.\)
Chứng minh rằng \(M< \frac{2}{3}\)
1/M=1/1+2+3+1/1+2+3+4+1/1+2+3+4+5+...+1/1+2+3+4+..+59
cmr M>2/3
