x*3,4=15,3

x = 15,3 : 3,4

x = 4,5

7,5:x=0,24

x = 7,5 : 0,24

x = 31,25

5/6:x=7/8

x = 5/6 : 7/8

x = 20/21

2/3*x=5/9

x = 5/9 : 2/3

x = 5/6

Xx3,4=15,3

X       = 15,3 : 3,4

X       =4.5

7,5:x=0,24

      x=7,5 : 0,24

      x= 31.25

5/6:x=7/8

      x=5/6 : 7/8

      x=  20/21

2/3xX=5/9

       X= 5/9 : 2/3

       X= 5/6

X x 3,4 = 15,3

x = 15,3 : 3,4

x = 4,5

7,5 : x = 0,24

x = 7,5 : 0,24

x = 31,25

5/6 : x = 7/8

x = 5/6 : /8

x = 20/21

2/3 x X = 5/9

x = 5/9 : 2/3

x = 5/6

`x xx 6/7=5/14`

`=>x=5/14:6/7`

`=>x=5/14xx7/6`

`=>x=35/84`

`=>x=5/12`

Vậy `x=5/12`

__

`x:2/3=4/9`

`=>x=4/9xx2/3`

`=>x=8/27`

Vậy `x=8/27`

__

`x-1/4=3/2`

`=>x=3/2+1/4`

`=>x=6/4+1/4`

`=>x=7/4`

Vậy `x=7/4`

__

`x+4/5=8/9`

`=>x=8/9-4/5`

`=>x=40/45-36/45`

`=>x=4/45`

Vậy `x=4/45`

\(x\cdot\dfrac{6}{7}=\dfrac{5}{14}\)

\(x\)         \(=\dfrac{5}{14}:\dfrac{6}{7}\)

\(x\)           \(=\dfrac{5}{12}\)

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

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

\(x\)          \(=\dfrac{8}{27}\)

\(x-\dfrac{1}{4}=\dfrac{3}{2}\)

\(x\)          \(=\dfrac{3}{2}+\dfrac{1}{4}\)

\(x\)            \(=\dfrac{7}{4}\)

\(x+\dfrac{4}{5}=\dfrac{8}{9}\)

\(x\)          \(=\dfrac{8}{9}-\dfrac{4}{5}\)

\(x\)            \(=\dfrac{4}{45}\)

Bài 1: 

a: x/-2=-18/x

=>x²=36

=>x=6 hoặc x=-6

b: x/2+x/5=17/10

=>7/10x=17/10

hay x=17/7

x + 9x + 7x + 5x = 2244

<=> 1x + 9x + 7x + 5x = 2244

x ( 1 + 9 + 7 + 5 ) = 2244

22x = 2244

x = 2244 : 22

x = 1122

x + 9x + 7x + 5x = 2244

<=> 22x = 2244

<=> x = 2244 : 22 

=> x = 102

Lộn :

x = 2244 : 22

x = 102

X- 9 = 21:5 

X- 9 = 4,2

x = 4,2 + 9

x = 13,2

X : 3 = 1,248 : 4

X : 3 = 0,312

x = 0,312 x 3

x = 0,936

x - 9 = 4,2

x = 4,2 + 9 =13,2

x : 3 = 0,312

x = 0,312 x 3 = 0,936

GIÚP MÌNH NHANH VỚI MỌI NGƯỜI ƠI 

Giải:

\(\dfrac{1}{3.5}+\dfrac{1}{5.7}+\dfrac{1}{7.9}+...+\dfrac{1}{x.\left(x+2\right)}=\dfrac{16}{99}\) 

\(\dfrac{1}{2}.\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{x.\left(x+2\right)}\right)=\dfrac{16}{99}\) 

\(\dfrac{1}{2}.\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{x}-\dfrac{1}{x+2}\right)=\dfrac{16}{99}\) 

                           \(\dfrac{1}{2}.\left(\dfrac{1}{3}-\dfrac{1}{x+2}\right)=\dfrac{16}{99}\) 

                                     \(\dfrac{1}{3}-\dfrac{1}{x+2}=\dfrac{16}{99}:\dfrac{1}{2}\) 

                                     \(\dfrac{1}{3}-\dfrac{1}{x+2}=\dfrac{32}{99}\) 

                                             \(\dfrac{1}{x+2}=\dfrac{1}{3}-\dfrac{32}{99}\) 

                                             \(\dfrac{1}{x+2}=\dfrac{1}{99}\) 

\(\Rightarrow x+2=99\) 

           \(x=99-2\) 

           \(x=97\) 

Chúc em học tốt!

\(\dfrac{1}{3x5}+\dfrac{1}{5x7}+\dfrac{1}{7x9}+...+\dfrac{1}{x\left(x+2\right)}=\dfrac{16}{99}\)

\(=\dfrac{1}{2}\left(\dfrac{2}{3x5}+\dfrac{2}{5x7}+...+\dfrac{2}{x\left(x+2\right)}\right)=\dfrac{16}{99}\)

\(=\dfrac{2}{3x5}\)\(+\dfrac{2}{5x7}+...+\dfrac{2}{x\left(x+2\right)}=\dfrac{32}{99}\)

\(=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}+.....+\dfrac{1}{x}-\dfrac{1}{x+2}=\dfrac{32}{99}\)

\(=\dfrac{1}{3}-\dfrac{1}{x+2}=\dfrac{32}{99}=>x=97\)

\(x+x\cdot3:\dfrac{2}{9}+x:\dfrac{2}{7}=252\)

\(\Leftrightarrow x+x\cdot3\cdot\dfrac{9}{2}+x\cdot\dfrac{7}{2}=252\)

\(\Leftrightarrow x\cdot18=252\)

hay x=14

dễ **** mình giải cho

a) \(547+389+453+211\)

\(=\left(547+453\right)+\left(389+211\right)\)

\(=1000+600\)

\(=1600\)

b) \(158+445+342+555\)

\(=\left(158+342\right)+\left(445+555\right)\)

\(=500+1000\)

\(=1500\)

c) \(24.3.5.10\)

\(=\left(24.5\right).\left(10.3\right)\)

\(=120.30\)

\(=3600\)

d) \(12.5.15.7\)

\(=\left(12.5\right).\left(15.7\right)\)

\(=60.105\)

\(=6300\)

e) \(1122.34+2244.83\)

\(=1122.2.17+2244.83\)

\(=2244.17+2244.83\)

\(=2244.\left(17+83\right)\)

\(=2244.100\)

\(=224400\)

f) \(8466.15+170.4233\)

\(=8466.15+85.2.4233\)

\(=8466.15+85.8466\)

\(=8466.\left(15+85\right)\)

\(=8466.100\)

\(=846600\)

A  1600

B 1500

C 3600

D 6300

\(a,547+389+453+211\)

\(=\left(547+453\right)+\left(389+211\right)\)

\(=1000+600\)

\(=1600\)

\(b,158+445+342+555\)

\(=\left(158+342\right)+\left(445+555\right)\)

\(=500+1000\)

\(=1500\)

\(c,24\times3\times5\times10\)

\(=\left(24\times5\right)\times\left(3\times10\right)\)

\(=120\times30\)

\(=3600\)

\(d,12\times5\times15\times7\)

\(=60\times105\)

\(=6300\)

\(e,1122\times34+2244\times83\)

\(=1122\times2\times17+2244\times83\)

\(=2244\times\left(17+83\right)\)

\(=2244\times100\)

\(=224400\)

\(f,8466\times15+170\times4233\)

\(=8466\times15+85\times2\times4233\)

\(=8466\times\left(15+85\right)\)

\(=8466\times100\)

\(=846600\)

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