\(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{63}>2\)

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1/2=1/2
1/3+1/4>1/4+1/4=1/2
1/5+…+1/8>4*1/8=1/2
1/9+…+1/16>8*1/16=1/2
1/2+1/3+1/4+…+1/16>4*1/2=2
1/2+1/3+1/4+…+1/63>1/2+1/3+1/4+…+1/16
=>  1/2+1/3+…+1/63>2

t i c k nhé !! 5756876876978080

12 tháng 6 2016

Ta có:

\(\frac{1}{2}=\frac{1}{2}\)

\(\frac{1}{3}+\frac{1}{4}>\frac{1}{4}+\frac{1}{4}=\frac{1}{2}\)

\(\frac{1}{5}+...+\frac{1}{8}>4.\frac{1}{8}=\frac{1}{2}\)

\(\frac{1}{9}+...+\frac{1}{16}>8.\frac{1}{16}=\frac{1}{2}\)

\(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{16}>4.\frac{1}{2}=2\)

\(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{63}>\frac{1}{2}+\frac{1}{3}+...+\frac{1}{16}\)

\(\Rightarrow\frac{1}{2}+\frac{1}{3}+...+\frac{1}{63}>2\)

16 tháng 1 2018

\(B=\frac{2016}{1}+\frac{2015}{2}+...+\frac{2}{2015}+\frac{1}{2016}\)

\(B=2016+\frac{2015}{2}+...+\frac{2}{2015}+\frac{1}{2016}\)

\(B=1+\left(\frac{2015}{2}+1\right)+...+\left(\frac{2}{2015}+1\right)+\left(\frac{1}{2016}+1\right)\)

\(B=\frac{2017}{2017}+\frac{2017}{2}+...+\frac{2017}{2015}+\frac{2017}{2016}\)

\(B=2017\left(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2016}+\frac{1}{2017}\right)\)

\(\frac{B}{A}=\frac{2017\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2016}+\frac{1}{2017}\right)}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2016}+\frac{2}{2017}}=2017\)

4 tháng 7 2016

|x| = 3/4 

=>  x= -3/4 ; 3/4

Mà x < 0

=>  x= -3/4

\(\left|x\right|=-1\frac{2}{5}\)

\(\Rightarrow x\in\varphi\)

|x| = 0,35 

=>  x = -0,35; 0,35

Mà x >0 

=> x= 0,35