\(\dfrac{1}{1-\dfrac{1}{21}}+\dfrac{1}{1+\dfrac{1}{1+2-1}}\)
\(=\dfrac{1}{\dfrac{20}{21}}+\dfrac{1}{1+\dfrac{1}{2}}\)
\(=\dfrac{21}{20}+\dfrac{1}{\dfrac{3}{2}}\)
\(=\dfrac{20}{21}+\dfrac{2}{3}=\dfrac{34}{21}\)
Tính :
a) \(\left(1+\dfrac{2}{3}-\dfrac{1}{4}\right).\left(\dfrac{4}{5}-\dfrac{3}{4}\right)^2\)
b) \(2:\left(\dfrac{1}{2}-\dfrac{2}{3}\right)^3\)
Bài 1:
a) A= \(\dfrac{5^2}{11.16}+\dfrac{5^2}{16.21}+\dfrac{5^2}{21.26}+...+\dfrac{5^2}{56.61}\)
b) B=\(-1-\dfrac{1}{3}-\dfrac{1}{6}-\dfrac{1}{10}-\dfrac{1}{15}-...-\dfrac{1}{1225}\)
Giúp mình với mình sắp KT rồi
\(A=\dfrac{1}{^{ }3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^{100}}\) và \(B=\dfrac{1}{2}\). Hãy so sánh chúng
rút gọn biểu thức :
N = 1 + \(\left(\dfrac{1}{2}\right)\) + \(\left(\dfrac{1}{2}\right)^2\) + \(\left(\dfrac{1}{2}\right)^3\) + ... + \(\left(\dfrac{1}{2}\right)^{100}\)
B=\(\dfrac{\dfrac{1}{2020}+\dfrac{1}{2021}-\dfrac{1}{2022}}{\dfrac{3}{2020}+\dfrac{3}{2021}-\dfrac{3}{2022}}-1\)
Rút gọn biểu thức:
P = \(\dfrac{1}{3}\) - \(\left(\dfrac{1}{3}\right)^2\) + \(\left(\dfrac{1}{3}\right)^3\) - \(\left(\dfrac{1}{3}\right)^4\) + ... + \(\left(\dfrac{1}{3}\right)^{19}\) - \(\left(\dfrac{1}{3}\right)^{20}\)
mọi người ơi giúp mik với ai làm đc mik tick cho
So sánh A với \(-\dfrac{1}{2}\) biết:
A=\(\left(\dfrac{1}{2^2}-1\right)\)\(\left(\dfrac{1}{3^2}-1\right)\left(\dfrac{1}{4^2}-1\right)...\left(1-\dfrac{1}{100^2}\right)\)
Tính
\(A=\left(1-\dfrac{1}{2^2}\right)\left(1-\dfrac{1}{3^2}\right)\left(1-\dfrac{1}{4^2}\right)...\left(1-\dfrac{1}{n^2}\right)\left(n\in N,n\ge2\right)\)
1 tính
a. \((\left|-5\right|7^4+3^2.2\dfrac{2}{5}):(7^5.125.7^3.50)\)
b. \((\dfrac{3^2}{9}.\dfrac{3^3}{81})^{12}:(\dfrac{3^6}{81^2})^{10}\)
c. \([(\dfrac{1}{2})^2.(\dfrac{1}{3})^4.\dfrac{2}{7}]:\left(\dfrac{1}{3}\right)^{-2}.\dfrac{-2^2}{7}\)
