$#Shả$

`A)=5/17xx(15/34+19/34)`

`=5/17xx1=5/17`

`B)=(13/12+7/12)+1/3`

`=5/3+1/3=2`

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a,=3/13.17/29.29/34

=3/13.1/2

=3/26

b,=(4/21+25/42).19/33

=11/14.19/33

=19/42

`a, = 3/13 xx (17/29 xx 29/34)`

`= 3/13 xx 1/2`

`= 3/26`.

`b, = 19/33(4/21 + 25/42)`

`= 19/33 xx ( 33/42 )`

`= 19/42`

$\frac{3}{13}\times \frac{17}{29})\times \frac{29}{34}$

     $=\frac{3}{13}\times \frac{17}{29}\times \frac{29}{34}$

     $=\frac{3\times 17\times 29}{13\times 29\times 34}$

     $=\frac{3\times 17\times 29}{13\times 29\times 2\times 17}$

     $=\frac{3}{13\times 2}$

     $=\frac{3}{26}$

`34,65+21,78+65,35+78,22`

`=(34,65+65,35)+(21,78+78,22)`

`=100+100=200`

`b)4,5xx5,5+4,7xx4,5`

`=4,5xx(5,5+4,7)`

`=4,5xx10,2`

`=4,5xx(10+0,2)`

`=4,5xx10+4,5xx0,2`

`=45+0,9=45,9`

`c)7,25xx2,5xx4`

`=7,25xx(2,5xx4)`

`=7,25xx10=72,5`

`34, 65 + 21,78 + 65,35 + 78, 22 `

`= (34, 65 +65,35 ) + ( 21,78 +78, 22 ) `

`=             100         +           100`

`=                              200`

`b. 4,5 xx 5,5 + 4,7 xx 4,5    `

`= 4,5 xx ( 5,5 + 4,7 ) `

`= 4,5 xx 10,2` 

`= 45,9`   

`c. 7,5 xx 2,5 xx 4 `

`= 7,5 xx ( 2,5 xx 4 ) `

`= 7,5 xx 10`

`=75`   

a) 13 x 5 x 2 = 13 x (5 x 2)

                    =   13 x 10

                     = 130

5 x 2 x 34 = (5 x 2) x 34

                 = 10 x 34

                  = 340

b) 2 x 26 x 5 = (2 x 5) x 26

                      = 10 x 26

                     = 260

a) 13 x 5 x 2                       5 x 2 x 34                                  b) 2 x 26 x 5

= 13 x ( 5 x 2 )                    = ( 5 x 2 ) x 34                             = ( 2 x 5 ) x 26

= 13 x 10                             = 10 x 34                                    = 10 x 26

= 130                                   = 340                                          = 260

Chúc bạn học tốt!

a) 13 x 5 x 2

= 13 x (5 x 2)

= 13 x 10 = 130

5 x 2 x 34

= (5 x 2 ) x 34

= 10 x 34 = 340

b) 2 x 26 x 5

= 26 x (2 x 5)

= 26 x 10 = 260

5 x 9 x 3 x 2

= (9 x 3) x (5 x 2)

= 27 x 10 = 270

`3/7+2/5+4/7`

`=(3/7+4/7)+2/5`

`=1+2/5`

`=5/5+2/5`

`=7/5`

`20/34+4/9+7/17`

`=(20/34+7/17)+4/9`

`=(20/34+14/34)+4/9`

`=34/34+4/9`

`=1+4/9`

`=9/9+4/9`

`=13/9`

`48xx2+96+48xx6`

`=48xx2+48xx2+48xx6`

`=48xx(2+2+6)`

`=48xx10`

`=480`

câu thứ hai thì làm như này em nhé:

    \(\dfrac{20}{34}\) + \(\dfrac{4}{9}\) + \(\dfrac{7}{17}\)

= (\(\dfrac{20}{34}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)

=  (\(\dfrac{10}{17}\) + \(\dfrac{7}{17}\)) + \(\dfrac{4}{9}\)

= 1 + \(\dfrac{4}{9}\)

= \(\dfrac{13}{9}\)

a,456*65+456*34+456

=456*65+456*34+456*1

=456*(65+34+1)

=456*100

=45600

a) = 456 x ( 65 + 34 + 1 )

     = 456 x 100

     = 45600

=(2.34).135+(17.2).80+650.34

=34.(135+135+80+650)

=34.900

=30600

Ta có:

=\(\dfrac{6x45x11x17}{15x12x34x33}\)

= \(\dfrac{6x15x3x11x17}{15x6x2x17x2x11x3}\)

= \(\dfrac{1}{2x2}\)

=\(\dfrac{1}{4}\)

Những chữ x ở trên là dấu nhân nhé