a) 4 + 5/7 = .... 28/7 + 5/7=.33/7..............

    5/9 x 6/7 = ..10/21....

    3 - 7/5 =  15/5 - 7/5...8/5........

    3/5 x 4/8 = ..3/10....

b) 2 - 1/4 = .8/4 - 1/4...7/4...

    4 : 5/9 = ..4 x 9/5 = 36/5....

    2/9 x 3/5 = .....2/15.....

    3/8 : 4 = ......3/8 x 1/4 = 3/2.....

a) \(4+\dfrac{5}{7}=\dfrac{4}{1}+\dfrac{5}{7}=\dfrac{28}{7}+\dfrac{5}{7}=\dfrac{33}{7}\)

   \(\dfrac{5}{9}\times\dfrac{6}{7}=\dfrac{10}{21}\)

    \(3-\dfrac{7}{5}=\dfrac{3}{1}-\dfrac{7}{5}=\dfrac{15}{5}-\dfrac{7}{5}=\dfrac{8}{5}\)

    \(\dfrac{3}{5}\times\dfrac{4}{8}=\dfrac{12}{40}=\dfrac{3}{10}\)

b) \(2-\dfrac{1}{4}=\dfrac{2}{1}-\dfrac{1}{4}=\dfrac{8}{4}-\dfrac{1}{4}=\dfrac{7}{4}\)

    \(4:\dfrac{5}{9}=\dfrac{4}{1}:\dfrac{5}{9}=\dfrac{4}{1}\times\dfrac{9}{5}=\dfrac{36}{5}\)

    \(\dfrac{2}{9}\times\dfrac{3}{5}=\dfrac{6}{45}=\dfrac{2}{15}\)

     \(\dfrac{3}{8}:4=\dfrac{3}{8}:\dfrac{4}{1}=\dfrac{3}{8}\times\dfrac{1}{4}=\dfrac{3}{2}\)

a) \(\dfrac{13}{6}\)b) \(\dfrac{7}{18}\)c) \(5\) d) \(\dfrac{2}{3}\)

1.

a)x\(=\)\(\dfrac{7}{6}\)\(-\dfrac{2}{3}\)

  x\(=\dfrac{1}{2}\)

b)x\(=\dfrac{9}{2}:\dfrac{3}{4}\)

   x\(=6\)

LỘN LỚP GÙI CÁI ĐẤY KIẾN THỨC LỚP 4 MÀ CỤ

`x + 2 3/4 = 5 2/3`

`=> x + 11/4 = 17/3`

`=> x= 17/3 -11/4`

`=>x=35/12`

__

`x - 1 4/5 = 3 2/7`

`=> x- 9/5 = 23/7`

`=> x= 23/7 +9/5`

`=>x=178/35`

__

`x xx 3 1/2 =4 3/4`

`=> x xx 7/2 =19/4`

`=> x= 19/4 : 7/2`

`=> x= 19/4 xx 2/7`

`=> x= 19/14`

__

`x : 2 2/3 = 4 1/3`

`=> x : 8/3 = 13/3`

`=> x= 13/3 xx 8/3`

`=>x=104/9`

a: =>x+11/4=17/3

=>x=17/3-11/4=68/12-33/12=35/12

b: =>x-9/5=23/7

=>x=23/7+9/5=178/35

c: =>x*7/2=4,75

=>x=19/4:7/2=19/14

d: =>x:8/3=13/3

=>x=13/3*8/3=104/9

a: \(=\dfrac{6}{7}\cdot\dfrac{-3}{5}=\dfrac{-18}{35}\)

b: \(=\dfrac{2}{5}\cdot\dfrac{-15}{8}=\dfrac{-30}{40}=-\dfrac{3}{4}\)

c: \(=\dfrac{2}{4}\cdot\dfrac{7}{3}=\dfrac{1}{2}\cdot\dfrac{7}{3}=\dfrac{7}{6}\)

d: \(=\dfrac{8}{3}\cdot\dfrac{16}{4}=\dfrac{128}{12}=\dfrac{32}{3}\)

a)-18/35

b)-3/4

c)7/6

d)32/3

e)5/21

sai thì xin lỗi nhé bn

a) \(\dfrac{-2}{3}+\dfrac{3}{4}=\dfrac{-8}{12}+\dfrac{9}{12}=\dfrac{1}{12}\)

b) \(\dfrac{5}{6}-\dfrac{-3}{5}=\dfrac{5}{6}+\dfrac{3}{5}=\dfrac{25}{30}+\dfrac{18}{30}=\dfrac{43}{30}\)

`a)` \(\dfrac{-2}{3}+\dfrac{3}{4}=\dfrac{-8}{12}+\dfrac{9}{12}=\dfrac{1}{12}\)

`b)` \(\dfrac{5}{6}-\dfrac{-3}{5}=\dfrac{5}{6}+\dfrac{3}{5}=\dfrac{25}{30}+\dfrac{18}{30}=\dfrac{43}{30}\)

a)\(\dfrac{-2}{3}+\dfrac{3}{4}=-\dfrac{8}{12}+\dfrac{9}{12}=\dfrac{1}{12}\)

b)\(\dfrac{5}{6}-\dfrac{-3}{5}=\dfrac{25}{30}-\dfrac{-18}{30}=\dfrac{25}{30}+\dfrac{18}{30}=\dfrac{43}{30}\)

a: \(=\dfrac{4+15}{20}\cdot\dfrac{1}{2}=\dfrac{19}{20}\cdot\dfrac{1}{2}=\dfrac{19}{40}\)

b: \(=\dfrac{13}{20}-\dfrac{1}{4}+\dfrac{5}{20}=\dfrac{18}{20}-\dfrac{1}{4}\)

\(=\dfrac{9}{10}-\dfrac{1}{4}=\dfrac{18}{20}-\dfrac{5}{20}=\dfrac{13}{20}\)

a) \(\dfrac{6}{7}+\dfrac{7}{8}=\dfrac{48}{56}+\dfrac{49}{56}=\dfrac{97}{56}\)

b) \(\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12}{15}-\dfrac{10}{15}=\dfrac{2}{15}\)

c) \(\dfrac{2}{3}.\dfrac{4}{9}=\dfrac{8}{27}\)

d) \(\dfrac{1}{5}:\dfrac{2}{7}=\dfrac{1}{5}.\dfrac{7}{2}=\dfrac{7}{10}\)

a: =48/56+49/56

=97/56

b: =12/15-10/15

=2/15

c: =(2*4)/(3*9)=8/27

d: =1/5*7/2=7/10

` 6/7 + 7/8 = 48/56 + 49/56 = 97/56`

` 4/5 - 2/3 = 12/15 - 10/15 = 2/15`

` 2/3 xx 4/9 = 8/27`

` 1/5 : 2/7 = 1/5 . 7/2 = 7/10`

b: \(=16-2\cdot4\cdot2\sqrt{5}+20-9-4\sqrt{5}\)

=27-20căn 5

a: 2-4căn 3<0

nên biểu thức ko có giá trị

\(b,\left(4-2\sqrt{5}\right)^2-\left(\sqrt{5}+2\right)^2\\ =\left[\left(4-2\sqrt{5}\right)-\left(\sqrt{5}+2\right)\right].\left[\left(4-2\sqrt{5}\right)+\left(\sqrt{5}+2\right)\right]=\left(2-3\sqrt{5}\right)\left(6-\sqrt{5}\right)\)

`b)(4-2\sqrt5)^2-(\sqrt5+2)^2`

`=(4-2\sqrt5-\sqrt5-2)(4-2\sqrt5+\sqrt5+2)`

`=(2-3\sqrt5)(6-\sqrt5)`

$---------$

Áp dụng HĐT :

`a^2-b^2=(a-b)(a+b)`

3/4 x 3/2 = 9/8

3/2 - 1/3 = 7/6

3/4x3/2=9/8

3/2-1/3=7/6

a, = 3/4 x 3/2 = 9/8

b, 3/2 - 1/3 = 7/6 

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