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30 tháng 7 2024

\(\dfrac{2}{3}+\dfrac{7}{4}:x=\dfrac{5}{6}\\ \Rightarrow\dfrac{7}{4}:x=\dfrac{5}{6}-\dfrac{2}{3}\\\Rightarrow\dfrac{7}{4}:x=\dfrac{1}{6} \\ \Rightarrow x=\dfrac{7}{4}:\dfrac{1}{6}\\ \Rightarrow x=\dfrac{21}{2}\)

Vậy \(x=\dfrac{21}{2}\)

30 tháng 7 2024

\(\dfrac{2}{3}+\dfrac{7}{4}:x=\dfrac{5}{6}\)

=> \(\dfrac{7}{4}:x=\dfrac{5}{6}-\dfrac{2}{3}\)

=> \(\dfrac{7}{4}:x=\dfrac{5}{6}-\dfrac{4}{6}\)

=> \(\dfrac{7}{4}:x=\dfrac{1}{6}\)

=> \(x=\dfrac{7}{4}:\dfrac{1}{6}\)

=> x = \(\dfrac{7}{4}.6\)

=> \(x=\dfrac{21}{2}\)

Vậy ...

18 tháng 6 2017

Ta có: \(\dfrac{a}{b}< \dfrac{c}{d}\Rightarrow ad< bc\)

\(\Rightarrow ad+cd< bc+dc\)

\(\Rightarrow d\left(a+c\right)< c\left(b+d\right)\)

\(\Rightarrow\dfrac{a+c}{b+d}< \dfrac{c}{d}\) (1)

\(ad< bc\)

\(\Rightarrow ad+ab< bc+ab\)

\(\Rightarrow a\left(b+d\right)< b\left(a+c\right)\)

\(\Rightarrow\dfrac{a}{b}< \dfrac{a+c}{b+d}\) (2)

Từ (1), (2) \(\Rightarrow\dfrac{a}{b}< \dfrac{a+c}{b+d}< \dfrac{c}{d}\left(đpcm\right)\)

18 tháng 6 2017

Ta có :

\(\dfrac{a}{b}< \dfrac{c}{d}\Rightarrow ad< bc\)

\(\Rightarrow ad+ab< bc+ab\Rightarrow a\left(d+b\right)< b\left(c+a\right)\)

\(\Rightarrow\dfrac{a}{b}< \dfrac{a+c}{b+d}\left(1\right)\)

Lại có :

\(ad< bc\Rightarrow ad+cd< bc+cd\Rightarrow d\left(a+c\right)< c\left(b+d\right)\)

\(\Rightarrow\dfrac{a+c}{b+d}< \dfrac{c}{d}\left(2\right)\)

Từ \(\left(1\right)+\left(2\right)\Leftrightarrow\dfrac{a}{b}< \dfrac{a+c}{b+d}< \dfrac{c}{d}\rightarrowđpcm\)

12 tháng 1 2018

2, \(\Rightarrow\left\{{}\begin{matrix}\\\dfrac{5}{4}x-\dfrac{7}{2}=0\\\dfrac{5}{8}x+\dfrac{3}{5}=0\\\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{14}{5}\\\\x=\dfrac{-24}{25}\\\end{matrix}\right.\)

30 tháng 8 2019

1) -2/3

1: \(\Leftrightarrow3x+4=2\)

=>3x=-2

=>x=-2/3

2: \(\Leftrightarrow7x-7=6x-30\)

=>x=-23

3: =>\(5x-5=3x+9\)

=>2x=14

=>x=7

4: =>9x+15=14x+7

=>-5x=-8

=>x=8/5

20 tháng 8 2017

Bn k có máy tính ạ/

20 tháng 8 2017

nóa pải ghi cách lm bn

19 tháng 11 2022

a: =>1/6x=-49/60

=>x=-49/60:1/6=-49/60*6=-49/10

b: =>3/2x-1/5=3/2 hoặc 3/2x-1/5=-3/2

=>x=17/15 hoặc x=-13/15

c: =>1,25-4/5x=-5

=>4/5x=1,25+5=6,25

=>x=125/16

d: =>2^x*17=544

=>2^x=32

=>x=5

i: =>1/3x-4=4/5 hoặc 1/3x-4=-4/5

=>1/3x=4,8 hoặc 1/3x=-0,8+4=3,2

=>x=14,4 hoặc x=9,6

j: =>(2x-1)(2x+1)=0

=>x=1/2 hoặc x=-1/2

5 tháng 8 2018

a. \(\dfrac{-39}{7}:x=26\)

x = \(\dfrac{-39}{7}:26\)

x = \(\dfrac{-3}{14}\)

b. \(x:\dfrac{13}{5}=\dfrac{7}{4}\)

x = \(\dfrac{7}{4}.\dfrac{13}{5}\)

x = \(\dfrac{91}{20}\)

c. x = \(\dfrac{-3}{5}-\dfrac{1}{2}\)

x = \(\dfrac{-11}{10}\)

d. \(x-\dfrac{3}{4}=\dfrac{9}{4}\)

x = \(\dfrac{9}{4}+\dfrac{3}{4}\)

x = 3

e. \(\dfrac{7}{8}:x=\dfrac{14}{3}\)

x = \(\dfrac{7}{8}:\dfrac{14}{3}\)

x = \(\dfrac{3}{16}\)

f. \(x:\dfrac{8}{3}=\dfrac{13}{3}\)

x = \(\dfrac{13}{3}.\dfrac{8}{3}\)

x = \(\dfrac{104}{9}\)

g. x = \(\dfrac{4}{10}-\dfrac{2}{5}\)

x = 0

chúc bạn học tốt banhquahahaleuleuok

26 tháng 7 2018

a) \(\dfrac{x}{48}=-\dfrac{4}{7}\Rightarrow x=-\dfrac{192}{7}\)

b) \(\left(x+\dfrac{4}{5}\right)-\dfrac{2}{5}=\dfrac{3}{5}\Rightarrow x+\dfrac{4}{5}=1\)

\(\Rightarrow x=\dfrac{1}{5}\)

c) \(2\left|x-1\right|^2=72\Rightarrow\left|x-1\right|^2=36\)

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

TH1: x - 1 = -6 => x = -5

TH2: x - 1 = 6 => x = 7

e) \(\dfrac{x}{2,5}=\dfrac{4}{5}\Rightarrow x=2\)

f) | x - 2 | = 1 + 4 = 5

TH1: x - 2 = -5 => x = -3

TH2: x - 2 = 5 => x = 7

26 tháng 7 2018

a) \(\dfrac{x}{48}=\dfrac{-4}{7}\)

⇒ x.7=48.(-4)

7x = -192

x=\(\dfrac{-192}{7}\) Vậy x=\(\dfrac{-192}{7}\)

b) \(\left(x+\dfrac{4}{5}\right)-\dfrac{2}{5}=\dfrac{3}{5}\)

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

\(x+\dfrac{4}{5}=1\)

\(x=1-\dfrac{4}{5}\)

\(x=\dfrac{1}{5}\)

c) chưa từng gặp dạng với giá trị tuyệt đối sory

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

\(\dfrac{1}{6}x=2+\dfrac{2}{3}\)

\(\dfrac{1}{6}x=\dfrac{8}{3}\)

\(x=\dfrac{8}{3}:\dfrac{1}{6}\)

\(x=16\)

e) \(\dfrac{x}{2,5}=\dfrac{4}{5}\)

=> x.5 = 4.2,5

5x=10

x=10:5

x=2

f) |x-2|-4=1

|x-2|=1+4

|x-2|=5

=>\(\left[{}\begin{matrix}x-2=5\\x-2=-5\end{matrix}\right.\) =>\(\left[{}\begin{matrix}x=5+2\\x=-5+2\end{matrix}\right.\) =>\(\left[{}\begin{matrix}x=7\\x=-3\end{matrix}\right.\)

đôi khi cũng có sai sót , hãy xem lại thật kĩ

Bài 1:

a: \(=\dfrac{1}{2}-\dfrac{7}{13}-\dfrac{1}{3}-\dfrac{6}{13}+\dfrac{1}{3}+\dfrac{4}{3}=\dfrac{4}{3}-1+\dfrac{1}{2}=\dfrac{1}{3}+\dfrac{1}{2}=\dfrac{5}{6}\)

b: \(=\dfrac{3}{4}+\dfrac{2}{5}+\dfrac{1}{9}-1-\dfrac{2}{5}+\dfrac{5}{4}=2-1+\dfrac{1}{9}=\dfrac{10}{9}\)

c: \(=\left(\dfrac{-3}{2}\cdot\dfrac{4}{3}\right)\cdot\dfrac{-9}{2}-\dfrac{1}{2}=9-\dfrac{1}{2}=8.5\)

2 tháng 8 2018

a, 1/3-3/4+3/5+1/4-2/9-1/36+1/15

=(1/3+3/5+1/15)-(3/4-1/4+2/9+1/36)

=1 - 3/4

=1/4

b, 3-1/4+2/3-5-1/3+6/5-6+7/4-3/2

=(3-5-6)-(1/4-7/4)+(2/3-1/3)+(6/5-3/2)

=-8 +3/2 +1/3 -3/10

=-97/15

a: \(\Leftrightarrow\dfrac{23}{5}\cdot\dfrac{50}{23}< =x< =\dfrac{-13}{5}:\dfrac{7}{5}\)

=>10<=x<=-13/7

hay \(x\in\varnothing\)

b: \(\Leftrightarrow-\dfrac{13}{3}\cdot\dfrac{1}{3}< =x< =\dfrac{-2}{3}\cdot\dfrac{-11}{12}\)

=>-13/9<=x<=22/36

hay \(x\in\left\{-1;0\right\}\)