tinh nhanh
B= -9/10 . 5/14 . + 1/10 . (-9/2 ) + 1/7 . (-9/10)
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HT
5
29 tháng 4 2019
\(D=\frac{-9}{10}.\frac{5}{14}+\frac{1}{10}.\left(\frac{-9}{2}\right)+\frac{1}{7}.\frac{-9}{10}\)
\(D=\frac{-9}{28}+\frac{-9}{20}+\frac{-9}{70}\)
\(D=\frac{-9}{10}\)
TD
3
8 tháng 5 2022
\(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\) \(\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
\(=\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
\(=\dfrac{45}{10}=\dfrac{9}{2}\)
TS
2
8 tháng 10 2016
\(1+2+3+4+5+6+7+8+9+10+11+12+13+14+15\)
\(=\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+10+\left(5+15\right)+\left(12+13+14+11\right)\)
\(=10+10+10+10+10+20+50\)
\(=120\)
8 tháng 10 2016
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15
=(1+9)+(2+8)+(3+7)+(6+4)+(5+15)+10+11+12+13+14
=10+10+10+10+20+10+11+12+13+14
=70+11+12+13+14
70+(11+12+13+14)
=70+50
=120
AY
22 tháng 5 2017
\(\frac{-9}{10}.\frac{5}{14}+\frac{1}{10}.\left(\frac{-9}{2}\right)+\frac{1}{7}.\frac{-9}{10}\)
\(=\frac{-9}{10}.\frac{5}{14}+\frac{1}{7}.\frac{-9}{10}+\frac{1}{10}.\left(\frac{-9}{2}\right)\)
\(=\frac{-9}{10}.\left(\frac{5}{14}+\frac{1}{7}\right)+\frac{1}{10}.\left(\frac{-9}{2}\right)\)
\(=\frac{-9}{10}.\frac{1}{2}+\frac{1}{10}.\left(\frac{-9}{2}\right)\)
\(=\left(\frac{-9}{10}+\frac{1}{2}\right)^2\)
\(=\left(\frac{-9}{10}+\frac{5}{10}\right)^2\)
\(=\left(\frac{-2}{5}\right)^2\)
\(=\frac{4}{25}\)
VB
2
7 tháng 1 2016
B = ( 2 - 4 - 6 + 8 ) + ( 10 - 12 - 14 + 16 ) +......+ ( 98 - 100 - 102 + 104 )
B = 0 + 0 +....+ 0 ( 52 số 0 )
B = 0
TN
7 tháng 1 2016
A=1+(3-5)+(7-9)+...+(2015-2017)
A=1+(-2)+(-2)+...+(-2)
A=(-2)*1008+1
A=(-2014)+1
A=-2015
T
0
27 tháng 7 2021
a) Ta có: \(\dfrac{-5}{7}\left(\dfrac{14}{5}-\dfrac{7}{10}\right):\left|-\dfrac{2}{3}\right|-\dfrac{3}{4}\left(\dfrac{8}{9}+\dfrac{16}{3}\right)+\dfrac{10}{3}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\)
\(=\dfrac{-5}{7}\cdot\dfrac{3}{2}\cdot\dfrac{21}{10}-\dfrac{3}{4}\cdot\dfrac{56}{3}+\dfrac{10}{3}\cdot\dfrac{8}{15}\)
\(=\dfrac{-9}{4}-14+\dfrac{16}{9}\)
\(=\dfrac{-1621}{126}\)
b) Ta có: \(\dfrac{17}{-26}\cdot\left(\dfrac{1}{6}-\dfrac{5}{3}\right):\dfrac{17}{13}-\dfrac{20}{3}\left(\dfrac{2}{5}-\dfrac{1}{4}\right)+\dfrac{2}{3}\left(\dfrac{6}{5}-\dfrac{9}{2}\right)\)
\(=\dfrac{-17}{26}\cdot\dfrac{13}{17}\cdot\dfrac{-3}{2}-\dfrac{20}{3}\cdot\dfrac{3}{20}+\dfrac{2}{3}\cdot\dfrac{-33}{10}\)
\(=\dfrac{3}{4}-1-\dfrac{11}{5}\)
\(=-\dfrac{49}{20}\)
\(B=\frac{-9}{10}.\frac{5}{14}+\frac{1}{10}.\frac{-9}{2}+\frac{1}{7}.\frac{-9}{10}\)
\(B=\frac{-9}{2}.\frac{1}{14}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-9}{28}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-27}{35}+\frac{-9}{70}\)
\(B=-\frac{9}{10}\)