\(\frac{-5}{7}\cdot\frac{9}{11}+\frac{-5}{7}\cdot\frac{2}{11}+\frac{5}{7}\)
K
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28 tháng 4 2019
a,\(\frac{3}{7}.\frac{4}{9}+\frac{3}{7}.\frac{5}{9}+\frac{5}{14}\)
\(=\frac{3}{7}.\left(\frac{4}{9}+\frac{5}{9}\right)+\frac{5}{14}\)
\(=\frac{3}{7}.1+\frac{5}{14}\)
\(=\frac{3}{7}+\frac{5}{14}=\frac{6}{14}+\frac{5}{14}=\frac{11}{14}\)
b,\(\frac{-11}{23}.\frac{6}{7}+\frac{8}{9}.\frac{-11}{23}-\frac{1}{23}\)
\(=\)\(\frac{-11}{23}.\left(\frac{6}{7}+\frac{8}{9}\right)-\frac{1}{23}\)
\(=\frac{-11}{23}.\frac{110}{63}-\frac{1}{23}\)
=\(\frac{-1210}{1449}\)-\(\frac{1}{23}\)
\(=\frac{-1273}{1449}\)
T
5 tháng 7 2019
#)Giải :
a)\(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{24.25}\)
\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{24}-\frac{1}{25}\)
\(=\frac{1}{5}-\frac{1}{25}\)
\(=\frac{4}{25}\)
b)\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)
\(=1-\frac{1}{101}\)
\(=\frac{100}{101}\)
XO
5 tháng 7 2019
a) \(\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{24.25}\)
= \(\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{24}-\frac{1}{25}\)
= \(\frac{1}{5}-\frac{1}{25}\)
= \(\frac{4}{25}\)
b) \(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{99.101}\)
= \(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{101}\)
= \(1-\frac{1}{101}\)
= \(\frac{100}{101}\)
c) \(5\frac{2}{7}.\frac{8}{11}+5\frac{2}{7}.\frac{5}{11}-5\frac{2}{7}.\frac{2}{11}\)
= \(5\frac{2}{7}.\left(\frac{8}{11}+\frac{5}{11}-\frac{2}{11}\right)\)
= \(5\frac{2}{7}\)
= \(\frac{37}{7}\)
PT
26 tháng 4 2017
kazuto kirigaya thật là bt làm ko đó ko bt thì nói đi còn bt thì làm đi
24 tháng 3 2019
a) A = \(\frac{19}{23}.\frac{-4}{27}-\frac{4}{23}.\frac{2}{7}\)
= \(\frac{19}{7}.\frac{-4}{23}+\frac{-4}{23}.\frac{2}{7}\)
= \(\frac{-4}{23}.\left(\frac{19}{7}+\frac{2}{7}\right)\)
= \(\frac{-4}{23}.3\)
= \(\frac{-12}{23}\)
b) B = \(\frac{3}{5}+\frac{2}{5}.\frac{-11}{3}+\frac{2}{3}.\frac{-2}{5}+\frac{14}{15}\)
= \(\frac{9+14}{15}+\frac{2}{5}.\frac{-11}{3}+\frac{-2}{3}.\frac{2}{5}\)
= \(\frac{23}{15}+\frac{2}{5}\left(\frac{-11}{3}+\frac{-2}{3}\right)\)
= \(\frac{23}{15}+\frac{2}{5}.\frac{-13}{3}\)
= \(\frac{23}{15}+\frac{-26}{15}\)
= \(\frac{-3}{15}=\frac{-1}{5}\)
\(\frac{-5}{7}.\frac{9}{11}+\frac{-5}{7}.\frac{2}{11}+\frac{5}{7}\)
\(=\frac{-5}{7}.\left(\frac{9}{11}+\frac{2}{11}\right)+\frac{5}{7}\)
\(=\frac{-5}{7}+\frac{5}{7}\)
\(=0\)
t tôi nhé
\(\frac{-5}{7}.\frac{9}{11}+\frac{-5}{7}.\frac{2}{11}+\frac{5}{7}\)
=\(\frac{-5}{7}.\left(\frac{9}{11}+\frac{2}{11}\right)+\frac{5}{7}\)
=\(\frac{-5}{7}.1+\frac{5}{7}\)
=\(\frac{-5}{7}+\frac{5}{7}\)
=\(0\)