KC
2
K
Khách
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28 tháng 3 2017
\(\dfrac{5}{7}x-x=1\dfrac{1}{7}\\ < =>\dfrac{5}{7}x-x=\dfrac{8}{7}\\ < =>\left(\dfrac{5}{7}-\dfrac{7}{7}\right)x=\dfrac{8}{7}\\ < =>-\dfrac{2}{7}x=\dfrac{8}{7}\\ =>x=\dfrac{\dfrac{8}{7}}{-\dfrac{2}{7}}=-4\)
2 tháng 5 2017
\(\dfrac{1}{7}.2\dfrac{1}{3}+\dfrac{5}{2}.\dfrac{3}{7}-\dfrac{59}{6}.\dfrac{1}{7}\)
=\(\dfrac{1}{7}.\dfrac{7}{3}+\dfrac{5}{2}.\dfrac{3}{7}-\dfrac{59}{6}.\dfrac{1}{7}\)
=\(\dfrac{1}{7}.\left(\dfrac{7}{3}-\dfrac{59}{6}\right)+\dfrac{5}{2}.\dfrac{3}{7}\)
=\(\dfrac{1}{7}.\dfrac{-15}{2}+\dfrac{5}{2}.\dfrac{3}{7}\)
=\(\dfrac{-15}{14}+\dfrac{15}{14}\)
= 0
LK
25 tháng 4 2018
a,
= \(\dfrac{20}{100}.\dfrac{15}{36}-\)(\(\dfrac{2}{5}+\dfrac{2}{3}\)):\(\dfrac{6}{5}\)
= \(\dfrac{20.15}{100.36}\)- ( \(\dfrac{6}{15}+\dfrac{10}{15}\)): \(\dfrac{6}{5}\)
= \(\dfrac{1.5}{5.12}-\dfrac{16}{15}:\dfrac{6}{5}\)
= \(\dfrac{1.1}{1.12}-\dfrac{16.5}{10.6}\)
= \(\dfrac{1}{12}-\dfrac{16.1}{2.6}\)
= \(\dfrac{1}{12}\) - \(\dfrac{16}{12}\)
= \(\dfrac{1}{12}+\dfrac{\left(-16\right)}{12}\)
= \(\dfrac{15}{12}\) = \(\dfrac{5}{4}\)
b,
= \(\dfrac{6}{7}+\dfrac{5}{4}+\dfrac{\left(-4\right)}{7}+\dfrac{25}{4}\)
= (\(\dfrac{6}{7}+\dfrac{\left(-4\right)}{7}\)) + (\(\dfrac{5}{4}+\dfrac{25}{4}\))
= \(\dfrac{2}{7}+\dfrac{30}{4}\)
= \(\dfrac{2}{7}+\dfrac{15}{2}\)
= \(\dfrac{4}{14}+\dfrac{105}{14}\)
= \(\dfrac{109}{14}\)
9 tháng 3 2017
a) \(\dfrac{5}{3}+\dfrac{3}{-4}+\dfrac{7}{6}\) \(\left(MC:12\right)\)
\(=\dfrac{20}{12}+\dfrac{-9}{12}+\dfrac{14}{12}\)
\(=\dfrac{20+\left(-9\right)+14}{12}\)
\(=\dfrac{25}{12}\)
b) \(\dfrac{-1}{5}+\dfrac{5}{3}+\dfrac{-3}{2}\) \(\left(MC:30\right)\)
\(=\dfrac{-6}{30}+\dfrac{50}{30}+\dfrac{-45}{30}\)
\(=\dfrac{\left(-6\right)+50+\left(-45\right)}{30}\)
\(=\dfrac{-1}{30}\)
c) \(\dfrac{2}{7}+\dfrac{-7}{5}+\dfrac{-2}{35}\) \(\left(MC:35\right)\)
\(=\dfrac{10}{35}+\dfrac{-49}{35}+\dfrac{-2}{35}\)
\(=\dfrac{10+\left(-49\right)+\left(-2\right)}{35}\)
\(=\dfrac{-41}{35}\)
d) \(3+\dfrac{-7}{2}+\dfrac{-1}{5}\) \(\left(MC:10\right)\)
\(=\dfrac{30}{10}+\dfrac{-35}{10}+\dfrac{-2}{10}\)
\(=\dfrac{30+\left(-35\right)+\left(-2\right)}{10}\)
\(=\dfrac{-7}{10}\)
9 tháng 3 2017
a) \(\dfrac{5}{3}+\dfrac{3}{-4}+\dfrac{7}{6}\)
\(=\dfrac{5}{3}+\dfrac{-3}{4}+\dfrac{7}{6}\)
\(=\) \(\dfrac{20}{12}+\dfrac{-9}{12}+\dfrac{14}{12}\)
\(=\dfrac{11}{12}+\dfrac{14}{12}\)
\(=\dfrac{25}{12}\)
b) \(\dfrac{-1}{5}+\dfrac{5}{3}+\dfrac{-3}{2}\)
\(=\dfrac{-6}{30}+\dfrac{50}{30}+\dfrac{-45}{30}\)
\(=\dfrac{44}{30}+\dfrac{-45}{30}\)
\(=\dfrac{-1}{30}\)
c) \(\dfrac{2}{7}+\dfrac{-7}{5}+\dfrac{-2}{35}\)
\(=\dfrac{10}{35}+\dfrac{-49}{35}+\dfrac{-2}{35}\)
\(=\dfrac{-39}{35}+\dfrac{-2}{35}\)
\(=\dfrac{-41}{35}\)
d) \(3+\dfrac{-7}{2}+\dfrac{-1}{5}\)
\(=\dfrac{3}{1}+\dfrac{-7}{2}+\dfrac{-1}{5}\)
\(=\dfrac{30}{10}+\dfrac{-35}{10}+\dfrac{-2}{10}\)
\(=\dfrac{-5}{10}+\dfrac{-2}{10}\)
\(=\dfrac{-7}{10}\)
H
11 tháng 4 2018
Giải:
\(\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{9.10}\)
\(=\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+...+\dfrac{1}{9}-\dfrac{1}{10}\)
\(=\dfrac{1}{3}-\dfrac{1}{10}\)
\(=\dfrac{7}{30}\)
Vậy ...
11 tháng 4 2018
\(\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\)
=\(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\)
=\(\dfrac{1}{3}-\dfrac{1}{10}\)
=\(\dfrac{7}{30}\)
PN
18 tháng 7 2017
a) \(6\dfrac{5}{7}-\left(1\dfrac{3}{4}+2\dfrac{5}{7}\right)\)
\(=6\dfrac{5}{7}-1\dfrac{3}{4}-2\dfrac{5}{7}\)
\(=\left(6\dfrac{5}{7}-2\dfrac{5}{7}\right)-1\dfrac{3}{4}\)
\(=4-1\dfrac{3}{4}\)
\(=3\dfrac{3}{4}\)
PN
18 tháng 7 2017
b) \(7\dfrac{5}{11}-\left(2\dfrac{3}{7}+3\dfrac{5}{11}\right)\)
\(=7\dfrac{5}{11}-2\dfrac{3}{7}-3\dfrac{5}{11}\)
\(=\left(7\dfrac{5}{11}-3\dfrac{5}{11}\right)-2\dfrac{3}{7}\)
\(=4-2\dfrac{3}{7}\)
\(=2\dfrac{3}{7}\)
KL
29 tháng 7 2017
A = \(\dfrac{1}{4}.\dfrac{7}{3}.12\)
= \(\dfrac{1.7.12}{4.3}\)
= \(7\)
@Nguyễn Thành Đăng
KL
29 tháng 7 2017
B = \(\dfrac{3}{8}.56.\dfrac{25}{7}.\left(-4\right)\)
= \(-\dfrac{3.56.25.4}{8.7}\)
= -3.100
= -300
@Nguyễn Thành Đăng
ND
1
2 tháng 5 2017
=\(\dfrac{6}{7}+\dfrac{5}{8}.\dfrac{1}{5}-\dfrac{3}{16}.\left(-4\right)\)
= \(\dfrac{6}{7}+\dfrac{5.1}{8.5}-\dfrac{3.\left(-4\right)}{16}\)= \(\dfrac{6}{7}+\dfrac{1}{8}-\dfrac{-3}{4}\)= \(\dfrac{48}{56}+\dfrac{7}{56}-\dfrac{-42}{56}\)
= \(\dfrac{48+7-\left(-42\right)}{56}\)=\(\dfrac{97}{56}\)
1/3 . 6/(-7) = -6/21 = -2/7
\(\dfrac{1}{3}\). \(\dfrac{6}{-7}\) = \(\dfrac{ }{7}\)
\(\dfrac{2}{-7}\) = \(\dfrac{ }{7}\)
\(◻\) = \(\dfrac{2}{-7}\) x 7
\(◻\) = \(-2\)