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CT
0
20 tháng 7 2016
\(\frac{3}{6.8}+\frac{3}{8.10}+.......+\frac{3}{198.200}\)
\(=\frac{3}{2}.\left(\frac{2}{6.8}+\frac{2}{8.10}+........+\frac{2}{198.200}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}+........+\frac{1}{198}-\frac{1}{200}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{6}-\frac{1}{200}\right)\)
\(=\frac{3}{2}.\frac{97}{600}=\frac{97}{400}\)
20 tháng 7 2016
\(3.\left(\frac{2}{6.8}+\frac{2}{8.10}+....+\frac{2}{198.200}\right).\frac{1}{2}\)
=\(3.\left(\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}+...+\frac{198}{200}\right).\frac{1}{2}\)
=\(3.\left(\frac{1}{6}-\frac{1}{200}\right).\frac{1}{2}\)
=.\(3.\frac{97}{600}.\frac{1}{2}\)=97/400
22 tháng 2 2017
12/5 -4/5 =8/5
11/6 -2/3 =21/18 =7/6
7/8 -2/7 =33/56
4 -8/5 =20/5-8/5 =12/5
2 -3/8 =16/8 -3/8 =13/8
16/7 -2 =16/7 -14/7 =2/7
25/4 -3=25/4 -12/4 =13/4
NV
22 tháng 2 2017
câu 2 : câu 3 :
a) 8/5 a)4 - 8/5 = 20/5 - 8/5 =12/5
b) 7/6 b)2 - 3/8 =16/8 - 3/8 = 13/8
c) 35/56 c)16/7 - 2 = 16/7 - 14/7 = 2/7
d)25/4 - 3 = 25/4 - 12/4 = 13/4
7 tháng 5 2020
\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}\)
\(=\frac{1}{2}-\frac{1}{14}\)
\(=\frac{3}{7}\)
PN
9 tháng 8 2020
\(\frac{2}{3}.\frac{4}{7}=\frac{8}{21}\)
\(\frac{3}{11}.2=\frac{6}{11}\)
\(4.\frac{2}{7}=\frac{8}{7}\)
\(\frac{8}{21}:\frac{2}{3}=\frac{8}{21}.\frac{3}{2}=\frac{21}{2.21}=\frac{1}{2}\)
\(\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)
\(\frac{3}{7}:\frac{3}{7}=\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)
PN
9 tháng 8 2020
lỡ tay bấm gửi trả lời luôn
\(\frac{2}{3}.\frac{1}{6}.\frac{9}{11}=\frac{2.9}{18.11}=\frac{2.9}{2.9.11}=\frac{1}{11}\)
\(\frac{2.3.4}{2.3.4.5}=\frac{6.4}{6.4.5}=\frac{24}{24.5}=\frac{1}{5}\)
16 tháng 6 2017
\(a.\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\)
\(=\frac{1}{2}-\frac{1}{5}\)
\(=\frac{3}{10}\)
\(b.\frac{2}{2\cdot3}+\frac{2}{3\cdot4}+\frac{2}{4\cdot5}\)
\(=2\left(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}\right)\)
\(=2\cdot\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\right)\)
\(=2\cdot\left(\frac{1}{2}-\frac{1}{5}\right)\)
\(=2\cdot\frac{3}{10}=\frac{3}{5}\)
\(c.\frac{1}{2\cdot3}+\frac{2}{3\cdot5}+\frac{3}{5\cdot8}\)
\(=\frac{1}{6}+\frac{2}{15}+\frac{3}{40}\)
\(=\frac{3}{8}\)
k nha 500 AE
DP
16 tháng 6 2017
a, \(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}\)
\(=\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\)
\(=\frac{1}{2}-\frac{1}{5}\)
\(=\frac{3}{10}\)
b, \(\frac{2}{2\times3}+\frac{2}{3\times4}+\frac{2}{4\times5}\)
\(=\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}\)
\(=\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\right)\times\frac{2}{1}\)
\(=\left(\frac{1}{2}-\frac{1}{5}\right)\times\frac{2}{1}\)
\(=\frac{3}{10}\times\frac{2}{1}\)
\(=\frac{3}{5}\)
c, \(\frac{1}{2\times3}+\frac{2}{3\times5}+\frac{3}{5\times8}\)
\(=\frac{3-2}{2\times3}+\frac{5-3}{3\times5}+\frac{8-5}{5\times8}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}\)
\(=\frac{1}{2}-\frac{1}{8}\)
\(=\frac{3}{8}\)
DL
1 tháng 6 2017
\(\frac{1}{2}:\frac{3}{2}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}\)
\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\)
\(=\frac{1\cdot\left(2\cdot5\cdot6\cdot7\right)}{8\cdot3\cdot\left(2\cdot5\cdot6\cdot7\right)}\)
\(=\frac{1}{24}\)
DL
1 tháng 6 2017
\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\cdot\frac{8}{9}\cdot\frac{9}{10}\)
\(=\frac{1\cdot\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)}{\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)\cdot10}\)
\(=\frac{1}{10}\)
9 tháng 2 2019
\(3+\frac{2}{5}-\frac{3}{4}\times\frac{4}{5}\)
\(=3+\frac{2}{5}-\frac{3}{4}\)
\(=\frac{3\times20+2\times4-3\times5}{20}\)
\(=\frac{60+8-15}{20}\)
\(=\frac{68-15}{20}\)
\(=\frac{53}{20}\)
9 tháng 2 2019
\(5-\frac{7}{9}+\frac{2}{3}-\frac{5}{6}:\frac{4}{9}\)
\(=5-\frac{7}{9}+\frac{2}{3}-\frac{45}{24}\)
\(=\frac{5\times72-7\times8+2\times24-45\times3}{72}\)
\(=\frac{360-56+48-135}{72}\)
\(=\frac{217}{72}\)
=\(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}\)
=\(\frac{1}{2}-\frac{1}{8}\)
=\(\frac{3}{8}\)