\(x\div\dfrac{2}{3}+\dfrac{4}{5}=\dfrac{8}{7}\times\dfrac{7}{10}\)

\(x\div\dfrac{2}{3}+\dfrac{4}{5}=\dfrac{4}{5}\)

\(x\div\dfrac{2}{3}=0\)

\(x=0\)

\(x\div\dfrac{2}{3}+\dfrac{4}{5}=\dfrac{8}{7}\cdot\dfrac{7}{10}\)

\(x\cdot\dfrac{3}{2}+\dfrac{4}{5}=\dfrac{4}{5}\)

\(x\cdot\dfrac{3}{2}=\dfrac{4}{5}-\dfrac{4}{5}=0\)

\(x=0\div\dfrac{3}{2}=0\)

Vậy x = 0

\(x\cdot\dfrac{3}{2}+\dfrac{4}{5}=\dfrac{8}{7}\cdot\dfrac{7}{10}\)

\(\dfrac{3}{2}x+\dfrac{4}{5}=\dfrac{4\cdot2\cdot7}{7\cdot2\cdot5}=\dfrac{4}{5}\)

\(\dfrac{3}{2}x=\dfrac{4}{5}-\dfrac{4}{5}=0\)

\(\Rightarrow x=0\)

\(\Leftrightarrow y\times\left(\dfrac{1}{7}+\dfrac{9}{21}+\dfrac{7}{3}\right)=\dfrac{5}{3}\)

\(\Leftrightarrow y\times\dfrac{61}{21}=\dfrac{5}{3}\)

\(\Leftrightarrow y=\dfrac{5}{3}:\dfrac{61}{21}=\dfrac{35}{61}\)

y x (1/7 +9/21 +7/3)= 5/3

y x 61/21 = 5/3

y = 5/3 : 61/21

y= 35/61

có ai giúp e với

1/ x=12

2/ x=10     nhớ tít đó nha

3/ x=-4

làm hẳn các bước đc ko các bạn

210 - 5 ( x - 10 ) = 200

5 ( x - 10 ) = 210 - 200

5 ( x - 10 ) = 10

x - 10 = 10 : 5

x - 10 = 2

x = 2 + 10

x = 12

( 5x - 39 ) . 7 + 3 = 80

( 5x - 39 ) . 7 = 80 - 3

( 5x - 39 ) . 7 = 77

5x - 39 = 77 : 7 

5x - 39 = 11

5x = 11 + 39

5x = 50

x = 50 : 5

x = 10

( 2x + 1 ) : 7 = 2³ + 3²

( 2x + 1 ) : 7 = 8 + 9

( 2x + 1 ) : 7 = 17

2x + 1 = 17 . 7

2x + 1 = 119

2x = 119 - 1

2x = 118

x = 118 : 2

x = 59

Huy làm sai r nhé

Thử lại:

(2. 59 + 1) = 119 : 7 = 17

\(B=\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}\)

   \(=9.\left(\frac{4}{1.3.5}+\frac{4}{3.5.7}+\frac{4}{5.7.9}+...+\frac{4}{25.27.29}\right)\)

    \(=9.\left(\frac{1}{1.3}-\frac{1}{3.5}+\frac{1}{3.5}-\frac{1}{5.7}+\frac{1}{5.7}-\frac{1}{7.9}+...+\frac{1}{25.27}-\frac{1}{27.29}\right)\)

    \(=9.\left(\frac{1}{3}-\frac{1}{675}\right)\)

    \(=9.\frac{224}{675}\)

    \(=\frac{224}{75}\)

THIẾU

\(=\frac{224}{75}< \frac{225}{75}=3\)

Vậy \(B< 3\)

mấy bọn nguuuuuuuuuuuuuuuuuu