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Y
6 tháng 6 2023
\(\dfrac{\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{23}}{\dfrac{2}{3}+\dfrac{2}{7}-\dfrac{2}{23}}\times\dfrac{\dfrac{1}{3}-0,25-0,2}{1\dfrac{1}{6}-0,875-0,7}\)
\(=\dfrac{\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{23}}{\dfrac{1}{3}+\dfrac{1}{3}+\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{23}-\dfrac{1}{23}}\times\dfrac{\dfrac{1}{3}-\dfrac{1}{4}-\dfrac{1}{5}}{\dfrac{7}{6}-\dfrac{7}{8}-\dfrac{7}{10}}\)
\(=\dfrac{\dfrac{1}{3} +\dfrac{1}{7}-\dfrac{1}{23}}{\dfrac{1}{3}\times2+\dfrac{1}{7}\times2-\dfrac{1}{23}\times2}\times\dfrac{\dfrac{2}{6}-\dfrac{2}{8}-\dfrac{2}{10}}{7\times\left(\dfrac{1}{6}-\dfrac{1}{8}-\dfrac{1}{10}\right)}\)
\(=\dfrac{\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{23}}{2\times\left(\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{23}\right)}\times\dfrac{2\times\left(\dfrac{1}{6}-\dfrac{1}{8}-\dfrac{1}{10}\right)}{7\times\left(\dfrac{1}{6}-\dfrac{1}{8}-\dfrac{1}{10}\right)}\)
\(=\dfrac{1}{2}\times\dfrac{2}{7}\)
\(=\dfrac{1}{7}\)
TD
2
16 tháng 6 2015
A = 6 -2/3 + 1 /2 - 5 -5/3 +3/2 -3 + 7/3 - 5/2
= (6 - 5 - 3) - ( 2/3 -5/3 + 7/3 ) + ( 1/2 +3/2 - 5/2)
= -2 + 0 -1/2 = -5/2
YN
21 tháng 6 2022
Dấu "^" của cậu nghĩa là phân số?
\(a,-1,75-\left(-\dfrac{1}{9}-2\dfrac{1}{18}\right)=-\dfrac{7}{4}-\left(-\dfrac{2}{18}-\dfrac{37}{18}\right)=-\dfrac{7}{4}+\dfrac{13}{6}=\dfrac{5}{12}\)
\(b,-\dfrac{1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)=-\dfrac{1}{12}-\dfrac{55}{24}=-\dfrac{19}{8}\)
\(c,-\dfrac{5}{6}-\left(-\dfrac{3}{8}+\dfrac{1}{30}\right)=-\dfrac{5}{6}+\dfrac{41}{120}=-\dfrac{59}{120}\)
S
17 tháng 1 2018
Đặt B = \(\frac{1}{4.9}+\frac{1}{9.14}+...+\frac{1}{44.49}\)
\(=\frac{1}{5}\left(\frac{5}{4.9}+\frac{5}{9.14}+...+\frac{5}{44.49}\right)\)
\(=\frac{1}{5}\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+...+\frac{1}{44}-\frac{1}{49}\right)\)
\(=\frac{1}{5}\cdot\left(\frac{1}{4}-\frac{1}{49}\right)=\frac{1}{5}\cdot\frac{45}{196}=\frac{9}{196}\)
Đặt C = \(\frac{1-3-5-....-49}{89}\)
\(=\frac{1-\left(3+5+...+49\right)}{89}\)
\(=\frac{1-\frac{\left(49+3\right).24}{2}}{89}\)
\(=\frac{1-624}{89}=\frac{-623}{89}=-7\)
\(\Rightarrow A=B.C=\frac{9}{196}\cdot\left(-7\right)=\frac{-9}{28}\)
9 tháng 4 2017
a, -7/2 + 3/4 - 17/2 = (-7/2 - 17/2) + 3/4 = -12 + 3/4 = -45/4 = -12,75.
9 tháng 4 2017
b, -1/12 - 21/8 + 1/3 = -1/12 + 1/3 - 21/8 = 1/4 - 21/8 = -19/8 = -2,375
\(\dfrac{1}{2}\) - \(\dfrac{43}{101}\) - \(\dfrac{1}{3}\) - \(\dfrac{1}{6}\)
= \(\dfrac{3}{6}\) - \(\dfrac{2}{6}\) - \(\dfrac{1}{6}\) - \(\dfrac{43}{101}\)
= - \(\dfrac{43}{101}\)
\(\dfrac{1}{2}\)-(-\(\dfrac{1}{3}\)) + \(\dfrac{1}{23}\) + \(\dfrac{1}{6}\)
= \(\dfrac{3}{6}\) + \(\dfrac{2}{6}\) + \(\dfrac{1}{6}\) + \(\dfrac{1}{23}\)
= 1 +1/23 = \(\dfrac{24}{23}\)