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1 tháng 5

1/3 + 13/19 - 4/9 + 6/19 + 5/18

= (13/19 + 6/19) - (1/3 + 4/9) + 5/18

= 1 - 7/9 + 5/18

= 1 - 14/18 + 5/18

= 13/18 + 5/18

= 1

\(=\dfrac{4}{19}\left(\dfrac{-5}{6}-\dfrac{7}{12}-\dfrac{10}{3}\right)\)

\(=\dfrac{4}{19}\cdot\left(\dfrac{-10-7-40}{12}\right)=\dfrac{4}{19}\cdot\dfrac{-57}{12}=-\dfrac{3}{3}=-1\)

2 tháng 4 2023

=\(\dfrac{4}{19}.\left(-\dfrac{5}{6}+-\dfrac{7}{12}\right)-\dfrac{40}{57}\)

=\(-\dfrac{4}{19}-\dfrac{40}{57}\)

=\(-\dfrac{52}{57}\)

10 tháng 3 2023

\(\dfrac{4}{5}\)+\(\dfrac{-5}{4}\)=\(\dfrac{0}{4}\)

\(\dfrac{-1}{3}\)+\(\dfrac{2}{5}-\dfrac{5}{6}\)=\(\dfrac{-10}{30}+\dfrac{12}{30}-\dfrac{25}{30}\)=\(\dfrac{-23}{30}\)

\(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}\)=\(\dfrac{2}{3}-\dfrac{2}{5}\)=\(\dfrac{10}{15}-\dfrac{6}{15}\)=\(\dfrac{4}{15}\)

 

10 tháng 3 2023

Gigachad cảm ơn bạn sai rồi

 

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

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

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

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

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

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

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

27 tháng 5 2021

Số số hạng của dãy là : (397−1):4+1=100(397-1):4+1=100 ( số )

⇒⇒ Có 100:2=50100:2=50 ( cặp )

1−5+9−13+....+393−3971-5+9-13+....+393-397

=(1−5)+(9−13)+....+(393−397)=(1-5)+(9-13)+....+(393-397)

=(−4)+(−4)+....+(−4)=(-4)+(-4)+....+(-4) 

=(−4).50=−200=(-4).50=-200

 TK
27 tháng 5 2021

`1-5+9-13+...+393-397`

`=(1-5)+(9-13)+...+(393-397)` (197 cặp)

`=(-4)+(-4)+...+(-4)` 

`=(-4) xx 197`

`=-788`

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

1: \(=-\dfrac{3}{4}+3-\dfrac{1}{4}-\dfrac{5}{4}+\dfrac{9}{2}=-\dfrac{9}{4}+3+\dfrac{9}{2}=\dfrac{-9+12+18}{4}=\dfrac{21}{4}\)

2: \(=\dfrac{-5}{7}\left(\dfrac{13}{19}+\dfrac{6}{19}\right)+\dfrac{5}{7}=\dfrac{-5}{7}+\dfrac{5}{7}=0\)

3: \(=\dfrac{2}{5}\left(1-\dfrac{8}{3}-\dfrac{5}{8}\right)=\dfrac{2}{5}\cdot\dfrac{-55}{24}=\dfrac{-11}{12}\)