c/m rằng : \(\dfrac{1}{65}\) <\(\dfrac{1}{5^3}\) +\(\dfrac{1}{6^3}\)+\(\dfrac{1}{7^3}\) +....+\(\dfrac{1}{2023^3}\) <\(\dfrac{1}{40}\)
biết a2 +ab+\(\dfrac{b^2}{3}\) =2023; c2+\(\dfrac{b^2}{3}\) =2000;a2+ac+c2=23 và a\(\ne\) 0;c\(\ne\)0;a\(\ne\) -c
c/m \(\dfrac{2c}{3}\) =\(\dfrac{b+c}{a+c}\)
Cho A = \(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{100^2}\)
CMR A < 1
Cho B \(=\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{2015}}\)
CMR: \(B< \dfrac{1}{2}\)
CMR: \(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{100^2}< 1\)
giúp mình với
Tính
a)\(P=1+\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+\dfrac{1}{4}\left(1+2+3+4\right)+...+\dfrac{1}{16}\left(1+2+3+...+16\right)\)
b)Cho a + b + c =2010 và \(\dfrac{1}{a+b}+\dfrac{1}{b+c}+\dfrac{1}{c+a}=\dfrac{1}{3}\) Tính \(S=\dfrac{a}{b+c}+\dfrac{b}{c+a}+\dfrac{c}{a+b}\)
Cho A= 1 + \(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{4034}\); B = 1 + \(\dfrac{1}{3}+\dfrac{1}{5}+\dfrac{1}{7}+...+\dfrac{1}{4033}\)
So sánh \(\dfrac{A}{B}\)với 1\(\dfrac{2017}{2018}\)
CMR \(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+...-\dfrac{1}{2000}+\dfrac{1}{2001}-\dfrac{1}{2002}=\dfrac{1}{1002}+...+\dfrac{1}{2002}\)
CMR: \(\dfrac{1}{3}+\dfrac{2}{3^2}+\dfrac{3}{3^3}+...+\dfrac{100}{3^{100}}< \dfrac{1}{2}\)