\(B=\left|157\dfrac{13}{27}-273\dfrac{7}{19}\right|-96\dfrac{14}{27}+15\dfrac{12}{19}\)
\(=273\dfrac{7}{19}-153\dfrac{13}{27}-96\dfrac{14}{27}+15\dfrac{12}{19}\)
\(=\left(273+15+\dfrac{7}{19}+\dfrac{12}{19}\right)-\left(153+96+\dfrac{13}{27}+\dfrac{14}{27}\right)\)
\(=289-250=39\)
Tính bằng cách hợp lí :
a , \(\dfrac{1}{15}+\dfrac{9}{10}+\dfrac{14}{15}-\dfrac{11}{9}-\dfrac{20}{10}+\dfrac{1}{157}\)
b , \(\dfrac{1}{5}-\dfrac{-1}{3}+\dfrac{-1}{5}-\dfrac{2}{6}\)
c , \(\dfrac{2}{1\times3}+\dfrac{2}{3\times5}+...+\dfrac{2}{2015\times2017}\)
d , \(\dfrac{5}{1\times3}+\dfrac{5}{3\times5}+...+\dfrac{5}{2015\times2017}\)
e , \(\dfrac{1}{1\times2}+\dfrac{1}{3\times4}+...+\dfrac{1}{2016\times2017}\)
\(\dfrac{-15}{4}\).\((-\dfrac{16}{25})\)
15.\(-(\dfrac{13}{10})\)
\((-\dfrac{14}{5})\).(-10)
\((\dfrac{3}{-10})\).-\((\dfrac{-15}{2})\)
SO SÁNH
Đặt A= \(\dfrac{3}{1^2.2^2}+\dfrac{5}{2^2.3^2}+\dfrac{7}{3^2.4^2}+...+\dfrac{39}{19^2-20^2}với1\)
Tính B=\(\left(1-\dfrac{2}{2.3}\right)\).\(\left(1-\dfrac{2}{3.4}\right).\left(1-\dfrac{2}{4.5}\right)......\left(1-\dfrac{2}{99.100}\right)\)
Cho R={3k-1| k∈R, -5≤ k ≤5}, S={x ∈R| \(3< \left|x\right|\le\dfrac{19}{2}\)}, T= {x∈R| 2x2-4x+2=0}. Tính \(R\cap S,S\cup T\),R\S
thức hiện hiện mỗi phép tính sau bằng hai cách
a)\(3\dfrac{4}{9}+5\dfrac{1}{6}\), b,\(8\dfrac{1}{14}-6\dfrac{3}{7}\) c,\(7-3\dfrac{6}{7}\)
\(A=\dfrac{2^{12}\cdot3^5-4^6\cdot9^2}{\left(2^2\cdot3\right)^6+8^4\cdot3^5}-\dfrac{5^{10}\cdot7^3-25^5\cdot49^2}{\left(125\cdot7\right)^3+5^9\cdot14^3}\)
\((\)\(\dfrac{-4}{5}\)).(-\(\dfrac{-25}{8}\))
\(\dfrac{5}{-14}\).(-\(\dfrac{7}{10}\))
Cho A= \(1+\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{4026}\) , B = \(1+\dfrac{1}{3}+\dfrac{1}{5}+\dfrac{1}{7}+....+\dfrac{1}{4025}\). So sánh \(\dfrac{A}{B}\) với \(1\dfrac{2013}{2014}\)
