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7 tháng 8 2019

a)x-5=7

=> x=9

b)2.x+6=24

=>2x=18

=>x=9

Tìm x :

a) \(x-5=49:7\)

\(\Leftrightarrow x-5=7\)

\(\Leftrightarrow x=7+5\)

\(\Leftrightarrow x=12\)

Vậy : \(x=12\)

b) \(2x+6=24\)

\(\Leftrightarrow2x=24-6=18\)

\(\Leftrightarrow x=18:2\)

\(\Leftrightarrow x=9\)

Vậy : \(x=9\)

c) \(\frac{1}{3}:x+\frac{1}{2}=5\)

\(\Leftrightarrow\frac{1}{3}:x=5-\frac{1}{2}=\frac{9}{5}\)

\(\Leftrightarrow x=\frac{1}{3}:\frac{9}{5}\)

\(\Leftrightarrow x=\frac{5}{27}\)

Vậy : \(x=\frac{5}{27}\)

d) \(\frac{1}{6}.x-\frac{1}{3}=2\)

\(\Leftrightarrow\frac{1}{6}.x=2-\frac{1}{3}=\frac{5}{3}\)

\(\Leftrightarrow x=\frac{5}{3}:\frac{1}{6}\)

\(\Leftrightarrow x=10\)

Vậy : \(x=10\)

e) \(\frac{x}{27}=\frac{3}{x}\)

\(\Leftrightarrow x.x=27.3\)

\(\Leftrightarrow x^2=81\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=9\end{matrix}\right.\)\(x\in N\)

\(\Rightarrow x=9\)

Vậy : \(x=9\)

g) \(1200:24-\left(17-x\right)=36\)

\(\Leftrightarrow50-17+x=36\)

\(\Leftrightarrow33+x=36\)

\(\Leftrightarrow x=36-33\)

\(\Leftrightarrow x=3\)

Vậy : \(x=3\)

h) \(674-\left(12+x\right)=427\)

\(\Leftrightarrow12+x=674-427=247\)

\(\Leftrightarrow x=247-12\)

\(\Leftrightarrow x=230\)

Vậy : \(x=230\)

k) \(36.\left(x-9\right)=900\)

\(\Leftrightarrow x-9=900:36\)

\(\Leftrightarrow x-9=25\)

\(\Leftrightarrow x=25+9\)

\(\Leftrightarrow x=34\)

m) \(1,2:x+3,8:x=2,5\)

\(\Leftrightarrow\left(1,2-3,8\right):x=2,5\)

\(\Leftrightarrow-2,6:x=2,5\)

\(\Leftrightarrow x=\frac{-2,6}{2,5}=-\frac{26}{25}\)

Vậy : \(x=-\frac{26}{25}\)

n) \(\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+\frac{1}{8.10}\right).x=\frac{1}{3}\)

\(\Leftrightarrow\frac{1}{2}.\left(\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}\right).x=\frac{1}{3}\)

\(\Leftrightarrow\left[\frac{1}{2}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}\right)\right].x=\frac{1}{3}\)

\(\Leftrightarrow\left[\frac{1}{2}.\left(1-\frac{1}{10}\right)\right].x=\frac{1}{3}\)

\(\Leftrightarrow\frac{1}{2}.\frac{9}{10}.x=\frac{1}{3}\)

\(\Leftrightarrow\frac{9}{20}.x=\frac{1}{3}\)

\(\Leftrightarrow x=\frac{1}{3}:\frac{9}{20}\)

\(\Leftrightarrow x=\frac{20}{27}\)

Vậy : \(x=\frac{20}{27}\)

1 tháng 2 2019

a) \(x-\frac{10}{3}=\frac{7}{15}\cdot\frac{3}{5}\)                          b) \(x+\frac{3}{22}=\frac{27}{121}\cdot\frac{11}{9}\)

\(\Leftrightarrow x-\frac{10}{3}=\frac{7}{25}\)                                \(\Leftrightarrow x+\frac{3}{22}=\frac{3}{11}\)

\(\Rightarrow x=\frac{7}{25}+\frac{10}{3}\)                                   \(\Rightarrow x=\frac{3}{11}-\frac{3}{22}\)

       \(x=\frac{271}{75}\)                                                  \(x=\frac{3}{22}\)

c) \(\frac{8}{23}.\frac{46}{24}-x=\frac{1}{3}\)                    d) \(1-x=\frac{49}{65}.\frac{5}{7}\)

        \(\Leftrightarrow\frac{2}{3}-x=\frac{1}{3}\)                      \(\Leftrightarrow1-x=\frac{7}{13}\)

                      \(\Rightarrow x=\frac{2}{3}-\frac{1}{3}\)                       \(\Rightarrow x=1-\frac{7}{13}\)

                           \(x=\frac{1}{3}\)                                         \(x=\frac{6}{13}\)

                                 

27 tháng 4 2019

Bài 2 :

1) \(x-70=-45\) 2) \(\frac{4}{7}:x=\frac{12}{28}\)

\(\Rightarrow\) \(x=-45+70\) \(\Rightarrow x=\frac{4}{7}:\frac{12}{28}\)

\(\Rightarrow\) \(x=25\) \(\Rightarrow x=\frac{4}{3}\)

Vậy \(x=25\) Vậy \(x=\frac{4}{3}\)

3) Giống câu c) ở bài 1

4) \(x-50=-35\) 5) \(\frac{4}{7}.x=\frac{11}{18}\)

\(\Rightarrow x=-35+50\) \(\Rightarrow x=\frac{11}{28}:\frac{4}{7}\)

\(\Rightarrow x=15\) \(\Rightarrow x=\frac{77}{72}\)

Vậy \(x=15\) Vậy \(x=\frac{77}{72}\)

6) \(\left(\frac{2}{3}x+2,5\right):2\frac{2}{6}=6\)

\(\Rightarrow\)\(\left(\frac{2}{3}x+2,5\right):\frac{14}{6}=6\)

\(\Rightarrow\) \(\frac{2}{3}x+2,5=6.\frac{14}{6}\)

\(\Rightarrow\frac{2}{3}x+2,5=14\)

\(\Rightarrow\frac{2}{3}x=\frac{23}{2}\)

\(\Rightarrow x=\frac{23}{2}:\frac{2}{3}\)

\(\Rightarrow x=\frac{69}{4}\)

Vậy \(x=\frac{69}{4}\)

27 tháng 4 2019

Bài 1:

1) \(\frac{7}{5}+\frac{-8}{5}=-\frac{1}{5}\)

2) \(-\frac{6}{5}.\frac{15}{24}=-\frac{3}{4}\)

3) \(\left(\frac{2}{3}+1,5\right)-3,5:7\frac{1}{2}=\)\(\frac{13}{6}-\frac{7}{15}=\frac{17}{10}\)

4) \(\frac{5}{8}-\frac{-7}{9}=\frac{5}{8}+\frac{7}{9}=\frac{101}{72}\)

5)\(\frac{-7}{3}.\frac{12}{28}=-1\)

28 tháng 10 2020

a, ( 152 +và 2/4 - 148 và 3/8 ) : 0,2 = x : 0,3

=>  33/8 : 1/5 = x : 3/10

=>  x : 3/10 = 165/8

=>  x = 99/10

b, ( 85 và 7/30 - 83 và 5/18 ) : 2 và 2/3 = 0,01x : 4

=>  88/45 : 8/3 = 0,01x : 4

=> 0,01x : 4 = 11/15

=> 0,01x = 44/15

=> x = 880/3

c, x - 1/ x + 5 = 6/7

=> 7( x - 1 ) = 6( x + 5 )

=> 7x - 7 = 6x + 30

=> 7x - 6x = 7 + 30

=> x = 37

d, x2/6 = 24/25

=> x2. 25 = 6 . 24

=> x2.25 = 144

=> x2 = 144/25

=> x = ( 12/5)2 hoặc x = ( -12/5)

g, x - 3/ x + 5 = 5/7

=> 7( x - 3 ) = 5 ( x + 5 )
=> 7x - 21 = 5x + 25

=> 7x - 5x = 21 + 25

=> 2x = 46

=> x = 23

25 tháng 6 2017

\(a,\)\(-\frac{3}{5}\cdot x=\frac{1}{4}+0,75\)

\(-\frac{3}{5}\cdot x=\frac{1}{4}+\frac{3}{4}=\frac{4}{4}=1\)

\(x=1\div\left(-\frac{3}{5}\right)\)

\(x=-\frac{5}{3}\)

\(b,\)\(\left(\frac{1}{7}-\frac{1}{3}\right)\cdot x=\frac{28}{5}\times\left(\frac{1}{4}-\frac{1}{7}\right)\)

\(\left(\frac{3}{21}-\frac{7}{21}\right)\cdot x=\frac{28}{5}\cdot\left(\frac{7}{28}-\frac{4}{28}\right)\)

\(-\frac{4}{21}\cdot x=\frac{28}{5}\cdot\frac{3}{28}\)

\(-\frac{4}{21}\cdot x=\frac{3}{5}\)

\(x=\frac{3}{5}\div\left(-\frac{4}{21}\right)\)

\(x=-\frac{63}{20}\)

25 tháng 6 2017

\(c,\)\(\frac{5}{7}\cdot x=\frac{9}{8}-0,125\)

\(\frac{5}{7}\cdot x=\frac{9}{8}-\frac{1}{8}\)

\(\frac{5}{7}\cdot x=1\)

\(x=1\div\frac{5}{7}\)

\(x=\frac{7}{5}\)

\(d,\)\(\left(\frac{2}{11}+\frac{1}{3}\right)\cdot x=\left(\frac{1}{7}-\frac{1}{8}\right)\cdot36\)

\(\left(\frac{6}{33}+\frac{11}{33}\right)\cdot x=\left(\frac{8}{56}-\frac{7}{56}\right)\cdot36\)

\(\frac{17}{33}\cdot x=\frac{1}{56}\cdot36\)

\(\frac{17}{33}\cdot x=\frac{9}{14}\)

\(x=\frac{9}{14}\div\frac{17}{33}\)

\(x=\frac{9}{14}\cdot\frac{33}{17}=\frac{297}{238}\)

13 tháng 6 2019

Bài 1:

a) \(\frac{2}{5}+\frac{1}{5}.\left(\frac{3}{4}\right)\)

= \(\frac{2}{5}+\frac{3}{20}\)

= \(\frac{11}{20}\)

b) \(\frac{5}{12}.\left(-\frac{3}{4}\right)\) + \(\frac{7}{12}.\left(-\frac{3}{4}\right)\)

= \(\left(\frac{5}{12}+\frac{7}{12}\right).\left(-\frac{3}{4}\right)\)

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

= \(-\frac{3}{4}\)

Còn câu c) đang nghĩ.

Bài 2:

a) \(\frac{5}{7}+\frac{2}{7}\)x = 1

1.x = 1

x = 1 : 1

x = 1

Vậy x = 1.

b) 0,2 + | x - 1, 3 = 1, 5|

0,2 + x = 1, 5 + 1, 3

0,2 + x = 2, 8

x = 2, 8 - 0, 2

x = 2, 6

Vậy x = 2, 6.

c) 2x + 5 = 37

2x = 37 - 5

2x = 32

2x = 25

=> x = 5

Vậy x = 5.

d) 2x + 2x + 1 = 48

2x . 1 + 2x . 21 = 48

2x . ( 1 + 2) = 48

2x . 3 = 48

2x = 48 : 3

2x = 16

2x = 24

=> x = 4

Vậy x = 4.

Chúc bạn học tốt!

13 tháng 6 2019

làm bước trung gian giùm mình luôn nhé

thanks trước những bạn làm giùm nhé

mình đang cần gấp lắm sáng mai là mình cần ai đang on làm giùm mình nhé

thanks

29 tháng 3 2020

Câu 6 :

a, Ta có : \(x+\frac{2x+\frac{x-1}{5}}{3}=1-\frac{3x-\frac{1-2x}{3}}{5}\)

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

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

=> \(15x+10x+\frac{5\left(x-1\right)}{5}=15-9x+\frac{3\left(1-2x\right)}{3}\)

=> \(15x+10x+x-1=15-9x+1-2x\)

=> \(15x+10x+x-1-15+9x-1+2x=0\)

=> \(37x-17=0\)

=> \(x=\frac{17}{37}\)

Vậy phương trình trên có nghiệm là \(S=\left\{\frac{17}{37}\right\}\)

Bài 7 :

a, Ta có : \(\frac{x-23}{24}+\frac{x-23}{25}=\frac{x-23}{26}+\frac{x-23}{27}\)

=> \(\frac{x-23}{24}+\frac{x-23}{25}-\frac{x-23}{26}-\frac{x-23}{27}=0\)

=> \(\left(x-23\right)\left(\frac{1}{24}+\frac{1}{25}-\frac{1}{26}-\frac{1}{27}\right)=0\)

=> \(x-23=0\)

=> \(x=23\)

Vậy phương trình trên có nghiệm là \(S=\left\{23\right\}\)

c, Ta có : \(\frac{x+1}{2004}+\frac{x+2}{2003}=\frac{x+3}{2002}+\frac{x+4}{2001}\)

=> \(\frac{x+1}{2004}+1+\frac{x+2}{2003}+1=\frac{x+3}{2002}+1+\frac{x+4}{2001}+1\)

=> \(\frac{x+2005}{2004}+\frac{x+2005}{2003}=\frac{x+2005}{2002}+\frac{x+2005}{2001}\)

=> \(\frac{x+2005}{2004}+\frac{x+2005}{2003}-\frac{x+2005}{2002}-\frac{x+2005}{2001}=0\)

=> \(\left(x+2005\right)\left(\frac{1}{2004}+\frac{1}{2003}-\frac{1}{2002}-\frac{1}{2001}\right)=0\)

=> \(x+2005=0\)

=> \(x=-2005\)

Vậy phương trình trên có nghiệm là \(S=\left\{-2005\right\}\)

e, Ta có : \(\frac{x-45}{55}+\frac{x-47}{53}=\frac{x-55}{45}+\frac{x-53}{47}\)

=> \(\frac{x-45}{55}-1+\frac{x-47}{53}-1=\frac{x-55}{45}-1+\frac{x-53}{47}-1\)

=> \(\frac{x-100}{55}+\frac{x-100}{53}=\frac{x-100}{45}+\frac{x-100}{47}\)

=> \(\frac{x-100}{55}+\frac{x-100}{53}-\frac{x-100}{45}-\frac{x-100}{47}=0\)

=> \(\left(x-100\right)\left(\frac{1}{55}+\frac{1}{53}-\frac{1}{45}-\frac{1}{47}\right)=0\)

=> \(x-100=0\)

Vậy phương trình trên có nghiệm là \(S=\left\{100\right\}\)

25 tháng 4 2018

a) x = 99/20

b) x = 7

c) x = 2

( chỉ lm đc đến đó thui nk )

14 tháng 10 2020

a) \(\left|2x+\frac{3}{4}\right|=\frac{1}{2}\)

     \(\orbr{\begin{cases}2x+\frac{3}{4}=\frac{1}{2}\\2x+\frac{3}{4}=\frac{-1}{2}\end{cases}}\) =>   \(\orbr{\begin{cases}2x=\frac{1}{2}-\frac{3}{4}\\2x=\frac{-1}{2}-\frac{3}{4}\end{cases}}\)  =>   \(\orbr{\begin{cases}2x=\frac{-1}{4}\\2x=\frac{-5}{4}\end{cases}}\) =>   \(\orbr{\begin{cases}x=\frac{-1}{8}\\x=\frac{-5}{8}\end{cases}}\)

Vậy \(x=\left\{\frac{-1}{8},\frac{-5}{8}\right\}\)

b) \(\frac{3x}{2,7}=\frac{\frac{1}{4}}{2\frac{1}{4}}\)\(\frac{3x}{2,7}=\frac{\frac{1}{4}}{\frac{9}{4}}\)

=> \(3x.\frac{9}{4}=2,7.\frac{1}{4}\)=>  \(\frac{27x}{4}=\frac{27}{40}\)

\(27x.40=27.4\)

\(1080.x=108\)

             \(x=\frac{1}{10}\)

Vậy \(x=\frac{1}{10}\)

c) \(\left|x-1\right|+4=6\)

\(\left|x-1\right|=6-4\)

\(\left|x-1\right|=2\)

\(\orbr{\begin{cases}x-1=2\\x-1=-2\end{cases}}\)=>  \(\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

Vậy \(x=\left[3,-1\right]\)

d) \(\frac{x}{3}=\frac{y}{5}=>\frac{y}{5}=\frac{x}{3}=>\frac{y-x}{5-3}=\frac{24}{2}=12\)

e) \(\left(x^2-3\right)^2=16\)

\(\left(x^2-3\right)^2=4^2\)\(=>x^2-3=4\)

\(x^2=7=>x=\sqrt{7}\)

Vậy \(x=\sqrt{7}\)

f) \(\frac{3}{4}+\frac{2}{5}x=\frac{29}{60}\)

               \(\frac{2}{5}x=\frac{29}{60}-\frac{3}{4}\) 

               \(\frac{2}{5}x=-\frac{4}{15}\)

          \(x=-\frac{4}{15}:\frac{2}{5}=-\frac{4}{15}.\frac{5}{2}=-\frac{2}{3}\)

Vậy \(x=-\frac{2}{3}\)

g) \(\left(-\frac{1}{3}\right)^3.x=\frac{1}{81}\)

\(\left(-\frac{1}{27}\right).x=\frac{1}{81}\)

\(x=\left(-\frac{1}{27}\right):\frac{1}{81}=\left(-\frac{1}{27}\right).81=-3\)

Vậy \(x=-3\)

k)\(\frac{3}{4}-\frac{2}{5}x=\frac{29}{60}\)

\(\frac{2}{5}x=\frac{3}{4}-\frac{29}{60}\)

\(\frac{2}{5}x=\frac{4}{15}\)

      \(x=\frac{2}{5}-\frac{4}{15}=>x=\frac{2}{15}\)

Vậy \(x=\frac{2}{15}\)

I) \(\frac{3}{5}x-\frac{1}{2}=-\frac{1}{7}\)

\(\frac{3}{5}x=-\frac{1}{7}+\frac{1}{2}\)

\(\frac{3}{5}x=\frac{5}{14}\)

\(x=\frac{5}{14}:\frac{3}{5}=\frac{5}{14}.\frac{5}{3}=\frac{25}{42}\)

Vậy \(x=\frac{25}{42}\)