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21 tháng 2 2018

\(3.\left(-4\right)^2+2.\left(-5\right)-20\)

\(=3.16+\left(-10\right)-20\)

\(=48-10-20\)

\(=18\)

20 tháng 2 2018

giúp mk với 

c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)

\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)

\(=1-2=-1\)

Giải:

a)-1/12+4/3=-1/12+16/12=15/12=5/4

b)(-4/14-3/15)-(1/5-20/35-(-1)).7

=-17/35-22/35.7

=-17/35-22/5

=-171/35

c)3/5+-5/20+30/75+-7/4

=3/5+-1/4+2/5+-7/4

=(3/5+2/5)+(-1/4+-7/4)

=1+-2

=-1

d)5/6.-12/14+7/13

=-5/7+7/13

=-16/91

e)2/-9-5/-36-1/4

=-1/12-1/4

=-1/3

f)2/23+-5/12+7/18+21/23+-7/12

=(2/23+21/23)+(-5/12+-7/12)+7/18

=1+-1+7/18

=7/18

\(\left(13\frac{4}{9}+2\frac{1}{9}\right)-3\frac{4}{9}\)

\(=\left(\frac{121}{9}+\frac{19}{9}\right)-\frac{31}{9}\)

\(=\frac{140}{9}-\frac{31}{9}\)

\(=\frac{109}{9}\)

 
18 tháng 4 2019

\(1,25\div\frac{15}{20}+\left(25\%-\frac{5}{6}\right)\div4\frac{2}{3}\)

\(=1,25\div\frac{3}{4}+\left(\frac{25}{100}-\frac{5}{6}\right)\div\frac{14}{3}\)

\(=1,25\times\frac{4}{3}+\left(\frac{6}{24}-\frac{20}{24}\right)\div\frac{14}{3}\)

\(=\frac{5}{3}+\frac{-14}{24}\times\frac{14}{3}\)

\(=\frac{60}{36}+\frac{-98}{36}\)

\(=\frac{-38}{36}=\frac{-19}{18}\)

16 tháng 4 2022

\(\dfrac{3}{7}.\left(-\dfrac{2}{5}\right).2\dfrac{1}{3}.20.\dfrac{19}{72}\)

\(=\dfrac{3}{7}.\left(-\dfrac{2}{5}\right).\dfrac{7}{3}.20.\dfrac{19}{72}\)

\(=\left(-\dfrac{6}{35}\right).\dfrac{7}{3}.20.\dfrac{19}{72}\)

\(=\left(-\dfrac{2}{5}\right).20.\dfrac{19}{72}\)

\(=\left(-8\right).\dfrac{19}{72}\)

\(=-\dfrac{19}{9}\)

6 tháng 1 2022

a, (-20) + 16 + (-34) + 20 = [(-20) + 20] + [16 + (-34)] = 0 + (-18) = (-18) b, 12 + 3.[39 - (5 - 2)2] = 12 + 3.[39 - 32] = 12 + 3.[39 - 9] = 12 + 3.30 = 12 + 90 = 102

9 tháng 3 2022
A= 3/5 . 5/4 - 1/4 ÷ 5/3 - 3/20
17 tháng 4 2016

\(\frac{3-\frac{1}{2}+\frac{1}{4}}{\frac{2}{3}-\frac{5}{6}-\frac{3}{4}}=\frac{\left(3-\frac{1}{2}+\frac{1}{4}\right)\left(3.4\right)}{\left(\frac{2}{3}-\frac{5}{6}-\frac{3}{4}\right)\left(3.4\right)}=\frac{36-6+3}{8-10-9}=\frac{33}{-11}=-3\)

=5/18+3/8*5/3

=5/18+5/8

=65/72

6 tháng 7 2023

\(\dfrac{5}{6}\cdot\dfrac{1}{3}+\dfrac{1}{2}\cdot\dfrac{3}{4}\cdot\dfrac{5}{3}\)

\(=\dfrac{5\cdot1}{6\cdot3}+\dfrac{1}{2}\cdot\dfrac{3\cdot5}{4\cdot3}\)

\(=\dfrac{5}{18}+\dfrac{1}{2}\cdot\dfrac{15}{12}\)

\(=\dfrac{5}{18}+\dfrac{1}{2}\cdot\dfrac{5}{4}\)

\(=\dfrac{5}{18}+\dfrac{1\cdot5}{2\cdot8}\)

\(=\dfrac{5}{18}+\dfrac{5}{8}\)

\(=\dfrac{65}{72}\)

\(\dfrac{5}{6}.\dfrac{1}{3}+\dfrac{5}{6}+\dfrac{3}{4}\)

\(=\dfrac{5}{6}.\left(\dfrac{1}{3}+\dfrac{3}{4}\right)=\dfrac{5}{6}.\dfrac{7}{12}=\dfrac{35}{72}\)