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29 tháng 10 2017
a) \(\dfrac{1,2}{x+3}=\dfrac{5}{4}\)
\(\Rightarrow\left(x+3\right).5=1,2.4\)
\(\Rightarrow\left(x+3\right).5=4,8\)
\(\Rightarrow x+3=4,8:5\)
\(\Rightarrow x+3=0,96\)
\(\Rightarrow x=-2,04\)
vậy \(x=-2,04\)
b)\(\dfrac{3}{5}:\dfrac{2x}{15}=\dfrac{1}{2}:\dfrac{4}{5}\)
\(\Rightarrow\dfrac{3}{5}:\dfrac{2x}{15}=\dfrac{5}{8}\)
\(\Rightarrow\dfrac{2x}{15}=\dfrac{3}{5}:\dfrac{5}{8}\)
\(\Rightarrow\dfrac{2x}{15}=\dfrac{24}{25}\)
\(\Rightarrow15.24=\left(2x\right).25\)
\(\Rightarrow360=\left(2x\right).25\)
\(\Rightarrow360:25=2x\)
\(\Rightarrow14,4=2x\)
\(\Rightarrow x=7,2\)
vậy \(x=7,2\)
29 tháng 10 2017
\(a,\dfrac{1,2}{x+3}=\dfrac{5}{4}\\ \left(x+3\right).5=1,2.4\\ 5x+8=4,8\\ 5x=4,8-8\\ 5x=-3,2\\ x=-3,2:5=-0,64\)
\(b,\dfrac{3}{5}:\dfrac{2x}{15}=\dfrac{1}{2}:\dfrac{4}{5}\\ \dfrac{2x}{15}=\dfrac{3}{5}\cdot\dfrac{4}{5}:\dfrac{1}{2}\\ \dfrac{2x}{15}=\dfrac{12}{25}.2\\ \dfrac{2x}{25}=\dfrac{24}{25}\\ 2x=\dfrac{24}{25}.5\\ 2x=\dfrac{24}{5}\\ x=\dfrac{24}{5}\cdot\dfrac{1}{2}=\dfrac{12}{5}\)
\(c,-\dfrac{4}{2,5}:3,5=1,5:x\\ x=3,5.1,5:\left(-\dfrac{4}{25}\right)\\ x=\dfrac{21}{4}\cdot\left(-\dfrac{25}{4}\right)=-\dfrac{525}{16}\)
\(d,0,12:3=2x:\dfrac{3}{5}\\ 2x=0,12\cdot\dfrac{3}{5}:3\\ 2x=\dfrac{9}{125}\cdot\dfrac{1}{3}\\ 2x=\dfrac{3}{125}\\ x=\dfrac{3}{125}\cdot\dfrac{1}{2}=\dfrac{3}{250}\)
24 tháng 9 2022
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
HH
18 tháng 6 2018
Giải:
a) \(\dfrac{1}{3}x+\dfrac{1}{5}-\dfrac{1}{2}x=1\dfrac{1}{4}\)
\(\Leftrightarrow\dfrac{1}{5}-\dfrac{1}{6}x=\dfrac{5}{4}\)
\(\Leftrightarrow\dfrac{1}{6}x=\dfrac{-21}{20}\)
\(\Leftrightarrow x=\dfrac{-63}{10}\)
Vậy ...
b) \(\dfrac{3}{2}\left(x+\dfrac{1}{2}\right)-\dfrac{1}{8}x=\dfrac{1}{4}\)
\(\Leftrightarrow\dfrac{3}{2}x+\dfrac{3}{4}-\dfrac{1}{8}x=\dfrac{1}{4}\)
\(\Leftrightarrow\dfrac{11}{8}x=\dfrac{-1}{2}\)
\(\Leftrightarrow x=\dfrac{-4}{11}\)
Vậy ...
Các câu sau làm tương tự câu b)
2 tháng 9 2017
a, \(\left|x+1,2\right|=0,5\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1,2=0,5\\x+1,2=-0,5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-0,7\\x=-1,7\end{matrix}\right.\)
Vậy ....
b, \(\left|x-\dfrac{1}{2}\right|+\dfrac{5}{6}=1\dfrac{1}{2}\)
\(\Leftrightarrow\left|x-\dfrac{1}{2}\right|=1\dfrac{1}{2}-\dfrac{5}{6}\)
\(\Leftrightarrow\left|x-\dfrac{1}{2}\right|=\dfrac{2}{3}\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{2}=\dfrac{2}{3}\\x-\dfrac{1}{2}=\dfrac{-2}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{6}\\x=\dfrac{-1}{6}\end{matrix}\right.\)
Vậy .....
c, \(\left|x-\dfrac{1}{2}\right|+\dfrac{4}{5}=\left|-3,2+\dfrac{2}{5}\right|\)
\(\left|x-\dfrac{1}{2}\right|+\dfrac{4}{5}=\left|-2,8\right|\)
\(\left|x-\dfrac{1}{2}\right|+\dfrac{4}{5}=2,8\)
\(\left|x-\dfrac{1}{2}\right|=2,8-\dfrac{4}{5}\)
\(\left|x-\dfrac{1}{2}\right|=2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{2}=2\\x-\dfrac{1}{2}=-2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=\dfrac{-8}{5}\end{matrix}\right.\)
Vậy ...
15 tháng 6 2022
a: |x-1/2|=7/2
=>x-1/2=7/2 hoặc x-1/2=-7/2
=>x=4 hoặc x=-3
b: \(x:\dfrac{3}{8}+\dfrac{5}{8}=x\)
=>8/3x-x=-5/8
=>5/3x=-5/8
hay x=-5/8:5/3=-5/8x3/5=-15/40=-3/8
c: \(\dfrac{5}{6}-\left|x-\dfrac{1}{2}\right|=\dfrac{15}{18}=\dfrac{5}{6}\)
=>|x-1/2|=0
=>x-1/2=0
hay x=1/2
e: \(\left(5x-3\right)^2-\dfrac{1}{64}=0\)
=>(5x-3)2=1/64
=>5x-3=1/8 hoặc 5x-3=-1/8
=>5x=25/8 hoặc 5x=23/8
=>x=5/8 hoặc x=23/40
12 tháng 1 2018
2, \(\Rightarrow\left\{{}\begin{matrix}\\\dfrac{5}{4}x-\dfrac{7}{2}=0\\\dfrac{5}{8}x+\dfrac{3}{5}=0\\\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{14}{5}\\\\x=\dfrac{-24}{25}\\\end{matrix}\right.\)
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 
\(\dfrac{3,7}{x}=\dfrac{-5}{1,2}\)
Ta có:
3,7 . 1,2 = x . (-5)
x = \(\dfrac{3,7.1,2}{-5}\)
x = \(\dfrac{111}{\dfrac{25}{-5}}\) = \(\dfrac{-111}{5}\)
Vậy x = \(\dfrac{-111}{5}\)