BT1: Tính nhanh:
1) \(\dfrac{5}{7}.\dfrac{-4}{19}-\dfrac{10}{7}.\dfrac{15}{38}\)
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15 tháng 5 2022
1: \(=\dfrac{16}{15}\left(-\dfrac{4}{9}+\dfrac{3}{7}\right)+\dfrac{16}{15}\left(\dfrac{4}{7}-\dfrac{5}{9}\right)\)
\(=\dfrac{16}{15}\left(-\dfrac{4}{9}+\dfrac{3}{7}+\dfrac{4}{7}-\dfrac{5}{9}\right)=0\)
2: \(=\dfrac{29}{9}\left(15+\dfrac{4}{7}-8-\dfrac{1}{7}+\dfrac{15}{7}-\dfrac{1}{7}\right)\)
\(=\dfrac{20}{9}\cdot\left(7\cdot\dfrac{18}{7}\right)=\dfrac{20}{9}\cdot18=40\)
16 tháng 4 2022
8: \(=\dfrac{-5}{9}-\dfrac{4}{9}+\dfrac{8}{15}+\dfrac{7}{15}-\dfrac{2}{11}=\dfrac{-2}{11}\)
9: =2/7-2/5+5/7=1-2/5=3/5
10: \(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}=\dfrac{-5}{19}\)
11: \(=\dfrac{-5}{7}\left(\dfrac{2}{11}+\dfrac{9}{11}\right)=\dfrac{-5}{7}\)
21 tháng 5 2022
1: \(=-\dfrac{7}{80}\cdot\dfrac{4}{7}-\dfrac{2}{9}:\dfrac{16}{3}+\dfrac{5}{24}\cdot\left(\dfrac{-50+38}{15}\right)^2\)
\(=\dfrac{-1}{20}-\dfrac{2}{9}\cdot\dfrac{3}{16}+\dfrac{5}{24}\cdot\dfrac{16}{25}\)
\(=\dfrac{-1}{20}-\dfrac{1}{24}+\dfrac{2}{15}\)
\(=\dfrac{-6-5+16}{120}=\dfrac{5}{120}=\dfrac{1}{24}\)
2: \(=1500-\left\{10^3-11\cdot\left[49-5\cdot8\right]\right\}\)
\(=1500-\left\{1000-11\cdot9\right\}\)
\(=1500-1000+99=599\)
Q
23 tháng 4 2017
\(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
\(=\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{7}.\dfrac{82}{5}\)
\(=\dfrac{4}{7}.\left(\dfrac{89}{5}-\dfrac{82}{5}\right)\)
\(=\dfrac{4}{7}.\dfrac{7}{5}\)
\(=\dfrac{4}{5}\)
\(\dfrac{5}{7}.\dfrac{-4}{19}+\dfrac{-15}{7}.\dfrac{5}{19}\)
\(=\dfrac{5}{7}.\dfrac{-4}{19}+\dfrac{5}{7}.\dfrac{-15}{19}\)
\(=\dfrac{5}{7}.\left(\dfrac{-4}{19}+\dfrac{-15}{19}\right)\)
\(=\dfrac{5}{7}.\left(-1\right)\)
\(=\dfrac{-5}{7}\)
28 tháng 5 2022
Sửa đề: \(M=\dfrac{\left(\dfrac{3}{10}-\dfrac{4}{15}-\dfrac{7}{20}\right)\cdot\dfrac{5}{19}}{\left(\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{-3}{35}\right)\cdot\dfrac{-4}{45}}\)
\(=\dfrac{\dfrac{3\cdot6-4\cdot4-7\cdot3}{60}\cdot\dfrac{5}{19}}{\dfrac{7+5+3}{35}\cdot\dfrac{-4}{45}}=\dfrac{\dfrac{-19}{60}\cdot\dfrac{5}{19}}{\dfrac{15}{35}\cdot\dfrac{-4}{45}}=\dfrac{-1}{12}:\dfrac{-4}{105}=\dfrac{105}{60}=\dfrac{7}{4}\)
10 tháng 3 2022
a: =9+7=16
b: =11+3/13-2-4/7-5-3/13
=4-4/7
=28/7-4/7=24/7
c: =2/7(5+1/4-3-1/4)=2/7x2=4/7
CM
26 tháng 9 2017
\(=7-\dfrac{4}{3}+\dfrac{1}{3}-6-\dfrac{5}{4}+\dfrac{4}{3}-5+\dfrac{7}{4}-\dfrac{5}{3}\)
\(=\left(7-6-5\right)-\left(\dfrac{4}{3}-\dfrac{4}{3}+\dfrac{5}{3}-\dfrac{1}{3}\right)-\left(\dfrac{5}{4}-\dfrac{7}{4}\right)\)
\(=-4-\dfrac{4}{3}-\left(\dfrac{-1}{2}\right)\)
\(=-4-\dfrac{4}{3}+\dfrac{1}{2}\)
\(=-\dfrac{24}{6}-\dfrac{8}{6}+\dfrac{3}{6}\)
\(=-\dfrac{32}{6}+\dfrac{3}{6}\)
\(=-\dfrac{29}{6}\)
R
27 tháng 1 2022
a) \(=\dfrac{157}{8}.\dfrac{12}{7}-\dfrac{61}{4}.\dfrac{12}{7}=\dfrac{12}{7}\left(\dfrac{157}{8}-\dfrac{61}{4}\right)=\dfrac{12}{7}.\dfrac{35}{8}=\dfrac{15}{2}\)
b) \(\dfrac{2}{5}.\dfrac{1}{3}-\dfrac{2}{15}\div\dfrac{1}{5}+\dfrac{3}{5}.\dfrac{1}{3}=\dfrac{1}{3}\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{2}{15}.5=\dfrac{1}{3}.1-\dfrac{2}{3}=\dfrac{1}{3}-\dfrac{2}{3}=-\dfrac{1}{3}\)
c) \(=-\dfrac{80}{9}\)
\(\dfrac{5}{7} *\dfrac{-4}{19}-\dfrac{5*2}{7}*\dfrac{15}{19*2} =\dfrac{5}{7}*(\dfrac{-4}{19}-\dfrac{15}{19}) =\dfrac{5}{7}*(\dfrac{-19}{19})=\dfrac{-5}{7}\)