2/5.1/3-2/15:1/5+3/5.1/3

 = ( 2/5 . 1/3 ) - ( 2/15 : 1/5 ) + (3/5 . 1/3 )

= 2/15 - 2/75 + 1/5

= 23/75

\(\frac{23}{75}\)
 

= 23 / 75 k đi

giúp mk với

. là dấu gì vậy bạn

\(\frac{2}{5}.\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}.\frac{1}{3}\)

\(=\left(\frac{2}{5}.\frac{1}{3}\right)-\left(\frac{2}{15}:\frac{1}{5}\right)+\left(\frac{3}{5}.\frac{1}{3}\right)\)

\(=\frac{2}{15}-\frac{2}{75}+\frac{1}{5}\)

\(=\frac{23}{75}\)

\(\frac{2}{5}:\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}.\frac{1}{3}\)

\(=\frac{6}{5}+\frac{-2}{3}+\frac{1}{5}\)

\(=\frac{11}{15}\)

~ Hok tốt ~

\(\frac{4}{2.4}+\frac{4}{4.6}+\frac{4}{6.8}+...+\frac{4}{2008.2010}\)

\(=4.\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+...+\frac{1}{2008.2010}\right)\)

\(=4.\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2008}-\frac{1}{2010}\right)\)

\(=4.\left[\frac{1}{2}+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{6}-\frac{1}{6}\right)+\left(\frac{1}{8}-\frac{1}{8}\right)+...+\left(\frac{1}{2008}-\frac{1}{2008}\right)-\frac{1}{2010}\right]\)

\(=4.\left[\frac{1}{2}-\frac{1}{2010}\right]\)

\(=4.\frac{502}{1005}=\frac{2008}{1005}\)

~ Hok tốt ~

b, \(\frac{4}{2.4}+\frac{4}{4.6}+\frac{4}{6.8}+...+\frac{4}{2008.2010}\)

\(=2\left(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{2008.2010}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{2008}-\frac{1}{2010}\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{2010}\right)\)

\(=2.\frac{502}{1005}\)

\(=\frac{1004}{1005}\)

Study well ! >_<

                                                                         Bài làm

1.

11 3/13 - ( 2 4/7 + 5 3/13 )

= 11 3/13 - 2 4/7 - 5 3/13

= ( 11 3/13 - 5 3/13 ) - 2 4/7

= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7

= ( 6 . 0 ) - 2 4/7

= 0 - 2 4/7

= 2 4/7

= 18/7

2 .

19 5/8 : 7/12 + ( -15 1/4) : 7/12

= { 19 5/8 + ( -15 1/4 ) } : 7/12

= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12

= { 4 . ( 5/8 + 2/8 ) } : 7/12

= ( 4 . 7/8 ) : 7/12

= 1.7/2 : 7/12

= 7/2 : 7/12

= 7/2 . 12/7

= 1.1/6.1

= 1/6

3 .

2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3

= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5

= 1/3 . 5/5 - 32/15 . 5/1

= 1/3 . 1 - 32.1/3.1

= 1/3 - 32/3

= -31/3

4 .

( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31

= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31

= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31

= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31

= 35/6 : 1/30 - 11/31

= 35/6 . 30/1 - 11/31

= 35.5/1.1 - 11/31

= 175 - 11/31

= 5425/31 - 11/31

= 5414/31

5.

75% - 1 1/5 + 0,5 : 5/12 - (-1/2)²

= 75/100 - 6/5 + 5/12 - 1/4

= 3/4 - 6/5 + 5/12 - 1/4

= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )

= 2/4 + ( 25/60 - 30/60 )

= 1/2 + (-5)/60

= 1/2 + (-1)/12

= 6/12 + (-1)/12

= 5/12

Đúng thì k cho mình nha !

1)

11 3/13 - ( 2 4/7 + 5 3/13 )

= 11 3/13 - 2 4/7 - 5 3/13

= ( 11 3/13 - 5 3/13 ) - 2 4/7

= { (11 - 5 ) . ( 3/13 - 3/13 ) } - 2 4/7

= ( 6 . 0 ) - 2 4/7

= 0 - 2 4/7

= 2 4/7

= 18/7

2 )

19 5/8 : 7/12 + ( -15 1/4) : 7/12

= { 19 5/8 + ( -15 1/4 ) } : 7/12

= [ { 19 + ( - 15) } . ( 5/8 + 1/4 ) ] : 7/12

= { 4 . ( 5/8 + 2/8 ) } : 7/12

= ( 4 . 7/8 ) : 7/12

= 1.7/2 : 7/12

= 7/2 : 7/12

= 7/2 . 12/7

= 1.1/6.1

= 1/6

3 )

2/5 . 1/3 - 2 2/15 : 1/5 + 3/5 . 1/3

= 1/3 . ( 2/5 + 3/5 ) - 2 2/15 : 1/5

= 1/3 . 5/5 - 32/15 . 5/1

= 1/3 . 1 - 32.1/3.1

= 1/3 - 32/3

= -31/3

4 )

( 3 1/3 + 2,5 ) : ( 3 1/6 - 4 1/5 ) - 11/31

= ( 10/3 + 25/10 ) : { ( 3 - 4 ) . ( 1/6 - 1/5 ) - 11/31

= ( 10/3 + 5/2 ) : { (-1) . ( 5/30 - 6/30 ) } - 11/31

= ( 20/6 + 15/6 ) : { (-1) . (-1)/30 } - 11/31

= 35/6 : 1/30 - 11/31

= 35/6 . 30/1 - 11/31

= 35.5/1.1 - 11/31

= 175 - 11/31

= 5425/31 - 11/31

= 5414/31

5)

75% - 1 1/5 + 0,5 : 5/12 - (-1/2)²

= 75/100 - 6/5 + 5/12 - 1/4

= 3/4 - 6/5 + 5/12 - 1/4

= ( 3/4 - 1/4 ) + ( 5/12 - 6/5 )

= 2/4 + ( 25/60 - 30/60 )

= 1/2 + (-5)/60

= 1/2 + (-1)/12

= 6/12 + (-1)/12

= 5/12

1=18/7

2=1/6

3=31/3

4=5414/31

5=5/12

a, \(\frac{2}{5}.\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}.\frac{1}{3}\)

\(=\frac{1}{3}.\left(\frac{2}{5}+\frac{3}{5}\right)-\frac{2}{15}.5\)

\(=\frac{1}{3}.1-\frac{2}{3}\)

\(=\frac{1}{3}-\frac{2}{3}\)

\(=\frac{-1}{3}\)

b, \(\left(6-2\frac{4}{5}\right).3\frac{1}{8}+1\frac{3}{8}:\frac{1}{4}\)

\(=\left(6-\frac{14}{5}\right).\frac{25}{8}+\frac{11}{8}.4\)

\(=\frac{16}{5}.\frac{25}{8}+\frac{11}{2}\)

\(=10+\frac{11}{2}\)

\(=\frac{31}{2}\)

1/3×(3/5+2/5)-2/15×1/5

1/3×1-2/15×1/5

1/3-2/15×1/5

1/3-2/75

25/75-2/75

23/75

(6-14/5)×25/8-11/8:4/1

16/5×25/8-11/8:4/1

10/1-11/8:4/1

10/1-11/8×1/4

10/1-11/32

320/32-11/32

309/32

a) \(\frac{8}{40}+\frac{-14}{35}-\frac{12}{60}\)

= \(\frac{1}{5}-\frac{2}{5}-\frac{1}{5}\)

= \(\left(\frac{1}{5}-\frac{1}{5}\right)-\frac{2}{5}\)

= \(-\frac{2}{5}\)

b) 5/7.5/11 + 5/7.5/11 - 5/7.14/11

= 5/7.(5/11 + 5/11 - 14/11) 

= 5/7.(-4/11)

= -20/77

c) \(19\frac{5}{8}:\frac{7}{12}-15\frac{1}{4}:\frac{7}{12}\)

= \(\left(19\frac{5}{8}-15\frac{1}{4}\right):\frac{7}{12}\)

=  \(\frac{35}{8}:\frac{7}{12}\)

=  \(\frac{15}{2}\)

d) 2/5.1/3 - 2/15 : 1/5 + 3/5.1/3

= (2/5 + 3/5).1/3 - 2/15 . 5

= 1.1/3 - 2/3

= 1/3 - 2/3

= -1/3

e) \(\frac{4}{9}.19\frac{1}{3}-\frac{4}{9}.39\frac{1}{3}\)

= \(\frac{4}{9}.\left(19\frac{1}{3}-39\frac{1}{3}\right)\)

= \(\frac{4}{9}.\left(-20\right)\)

= \(\frac{-80}{9}\)

g) \(\frac{81.17-15.81}{81.17-81.15}\)

= 1

a)8/40+-14/35-12/60=1/5+(-2/5)-1/5=-2/5

b)5/7.5/11+5/7.5/11-5/7.14/11=5/7.(5/11+5/11-14/11)=5/7.-4/11=-20/77

c)19 5/8:7/12-15 1/4:7/12=(19 5/8-15 1/4):7/12=35/8.12/7=15/2

d)2/5.1/3-2/15:1/5+3/5.1/3=2/15-2/15.5/1+3/15=2/15.2/3+1/5=-5/15=-1/5

e)4/9.19 1/3-4/9.39 1/3=4/9.(19 1/3- 39 1/3)=4/9. 20=80/9

g)81.17-15.81/81.17-81.15=81.(17-15)-15.1.17=81.2-255=162-255=-90

Chúc bạn học giỏi!!! hihi