\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}\)
\(=\left(\frac{1}{41}+\frac{1}{42}+...+\frac{1}{60}\right)+\left(\frac{1}{61}+\frac{1}{62}+...+\frac{1}{80}\right)>\frac{1}{60}.20+\frac{1}{80}.20\)
\(>\frac{1}{3}+\frac{1}{4}=\frac{7}{12}\)
Chứng tỏ rằng: \(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
Chứng tỏ rằng :\(y=\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
chứng tỏ rằng :
\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
Chứng minh rằng :\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
A = 9999931999 - 5555571997 CMR CHIA HẾT CHO 5
Chứng tỏ rằng : \(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+......+\frac{1}{79}+\frac{1}{80}\) < \(\frac{7}{12}\)
Ai Đúng tk
Cm: \(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
Chứng minh rằng:
a)\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
b)\(\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+...+\frac{1}{2^n}<1\)
CM::
\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+\frac{1}{44}+............+\frac{1}{79}+\frac{1}{80}>\frac{7}{12}\)
Hãy chứng tỏ rằng :
\(\frac{1}{41}\)+ \(\frac{1}{42}\)+ \(\frac{1}{43}\)+ ..... + \(\frac{1}{79}\)+ \(\frac{1}{80}\)> \(\frac{7}{12}\)
Các bn làm giúp mk vs, bài này khó, nghĩ mãi ko ra
