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DL
3
30 tháng 7 2020
(2/5-3/4)-2/5
-7/20-2/5
-3/4
-10/11.4/7+-10/7.3/7+21/11
-10/11.(4/7+3/7)+21/11
-10/11.1+21/11
-10/11+21/11
1
T
30 tháng 7 2020
\(a,\left(\frac{2}{5}-\frac{3}{4}\right)-\frac{2}{5}\)
\(=\frac{2}{5}-\frac{3}{4}-\frac{2}{5}\)
\(=\frac{2}{5}-\frac{2}{5}-\frac{3}{4}\)
\(=0-\frac{3}{4}\)
\(=-\frac{3}{4}\)
\(b,\frac{-10}{11}.\frac{4}{7}+\frac{-10}{11}.\frac{3}{7}+1\frac{10}{11}\)
\(=\frac{-10}{11}.\left(\frac{4}{7}+\frac{3}{7}\right)+1\frac{10}{11}\)
\(=\frac{-10}{11}+1+\frac{10}{11}\)
\(=\left(\frac{-10}{11}+\frac{10}{11}\right)+1\)
\(=1\)
Học tốt
MV
27 tháng 4 2017
1)
a)
\(\dfrac{-5}{11}\cdot\dfrac{4}{7}+\dfrac{-5}{11}\cdot\dfrac{3}{7}-\dfrac{8}{11}\\ =\dfrac{-5}{11}\cdot\left(\dfrac{4}{7}+\dfrac{3}{7}\right)-\dfrac{8}{11}\\ =\dfrac{-5}{11}\cdot1-\dfrac{8}{11}\\ =\dfrac{-5}{11}-\dfrac{8}{11}\\ =\dfrac{-5}{11}+\dfrac{-8}{11}\\ =\dfrac{-13}{11}\)
b)
\(\left(\dfrac{2}{9}:\dfrac{5}{3}+\dfrac{1}{3}:\dfrac{5}{3}\right)^2-\left(\dfrac{1}{3}-\dfrac{5}{8}\right)\\ =\left(\dfrac{2}{9}\cdot\dfrac{3}{5}+\dfrac{1}{3}\cdot\dfrac{3}{5}\right)^2-\left(\dfrac{-7}{24}\right)\\ =\left[\dfrac{3}{5}\cdot\left(\dfrac{2}{9}+\dfrac{1}{3}\right)\right]^2+\dfrac{7}{24}\\ =\left[\dfrac{3}{5}\cdot\dfrac{5}{9}\right]^2+\dfrac{7}{24}\\ =\left[\dfrac{1}{3}\right]^2+\dfrac{7}{24}\\ =\dfrac{1}{9}+\dfrac{7}{24}\\ =\dfrac{29}{72}\)
c) \(14-\left|\dfrac{-3}{4}\right|-\left(\dfrac{1}{3}-\dfrac{5}{8}\right)\\ =14-\dfrac{3}{4}-\left(\dfrac{-7}{24}\right)\\ =14+\dfrac{-3}{4}+\dfrac{7}{24}\\ =13\dfrac{13}{24}\)
VS
2
23 tháng 6 2020
\(\frac{5}{11}.\frac{4}{9}+\frac{5}{11}.\frac{8}{9}-\frac{5}{11}.\frac{1}{9}\)
\(=\frac{5}{11}\left(\frac{4}{9}+\frac{8}{9}-\frac{1}{9}\right)\)
\(=\frac{5}{11}.\frac{11}{9}=\frac{5}{9}\)
30 tháng 4 2020
\(\frac{11.4-11}{2-13}\)
\(=\frac{11\left(4-1\right)}{-11}\)
\(=\frac{3}{-1}\)
\(=-3\)
KT
12 tháng 8 2018
mạo phép chỉnh đề:
\(\frac{3x}{2.5}+\frac{3x}{5.8}+\frac{3x}{8.11}+\frac{3x}{11.14}=\frac{1}{21}\)
<=> \(x\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}\right)=\frac{1}{21}\)
<=> \(x\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}\right)=\frac{1}{21}\)
<=> \(x\left(\frac{1}{2}-\frac{1}{14}\right)=\frac{1}{21}\)
<=> \(x.\frac{3}{7}=\frac{1}{21}\)
<=> \(x=\frac{1}{9}\)
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