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12 tháng 1 2018
2, \(\Rightarrow\left\{{}\begin{matrix}\\\dfrac{5}{4}x-\dfrac{7}{2}=0\\\dfrac{5}{8}x+\dfrac{3}{5}=0\\\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{14}{5}\\\\x=\dfrac{-24}{25}\\\end{matrix}\right.\)
CN
3 tháng 1 2018
\(\left(\dfrac{2}{5}+\dfrac{1}{4}\right)\left(\dfrac{-x}{3}+\dfrac{1}{2}\right)+\dfrac{2}{3}=\dfrac{7}{4}\)
⇔ \(\dfrac{13}{20}\left(\dfrac{-x}{3}+\dfrac{1}{2}\right)=\dfrac{7}{4}-\dfrac{2}{3}\)
⇔ \(\dfrac{13}{20}\left(\dfrac{-x}{3}+\dfrac{1}{2}\right)=\dfrac{13}{12}\)
⇔ \(\dfrac{-x}{3}+\dfrac{1}{2}=\dfrac{13}{12}:\dfrac{13}{20}\)
⇔ \(\dfrac{-x}{3}+\dfrac{1}{2}=\dfrac{5}{3}\)
⇔ \(\dfrac{-x}{3}=\dfrac{5}{3}-\dfrac{1}{2}\)
⇔ \(\dfrac{-x}{3}=\dfrac{7}{6}\)
⇔ \(\dfrac{-2x}{6}=\dfrac{7}{6}\)
⇔ -2x = 7
⇔ \(x=-\dfrac{7}{2}\)
b) \(\left(\dfrac{3}{5}-\dfrac{x}{2}\right)\left(\dfrac{4}{5}+\dfrac{1}{2}\right)-\dfrac{4}{3}=\dfrac{3}{2}\)
⇔ \(\dfrac{13}{10}\left(\dfrac{3}{5}-\dfrac{x}{2}\right)=\dfrac{3}{2}+\dfrac{4}{3}\)
⇔ \(\dfrac{13}{10}\left(\dfrac{3}{5}-\dfrac{x}{2}\right)=\dfrac{17}{6}\)
⇔ \(\dfrac{3}{5}-\dfrac{x}{2}=\dfrac{17}{6}:\dfrac{13}{10}\)
⇔ \(\dfrac{3}{5}-\dfrac{x}{2}=\dfrac{85}{39}\)
⇔ \(\dfrac{x}{2}=\dfrac{3}{5}-\dfrac{85}{39}\)
⇔ \(\dfrac{x}{2}=\dfrac{-308}{195}\)
⇔ \(\dfrac{195x}{390}=\dfrac{-616}{390}\)
⇔ 195x = -616
⇔ \(x=\dfrac{-616}{195}\)
19 tháng 9 2017
\(\dfrac{5}{6}x-\dfrac{3}{4}=\dfrac{-1}{4}+\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{5}{6}x=\dfrac{7}{6}\)
\(\Rightarrow x=\dfrac{7}{5}\)
b) \(-1\dfrac{1}{2}-\dfrac{2}{3}x=\dfrac{5}{6}-\left(\dfrac{-2}{5}\right)\)
\(\Leftrightarrow\dfrac{2}{3}x=-\dfrac{41}{15}\)
\(\Rightarrow x=-\dfrac{41}{10}\)
c) \(\left(\dfrac{4}{5}:x+1,5\right):\dfrac{2}{3}=-1,5\)
\(\Leftrightarrow\dfrac{8+15x}{10x}.\dfrac{3}{2}=\dfrac{-3}{2}\)
\(\Leftrightarrow\dfrac{24+45x}{20x}=\dfrac{-3}{2}\)
\(\Leftrightarrow-60x=48+90x\)
\(\Rightarrow x=-0,32\)
d) \(\dfrac{4}{3}x-\dfrac{2}{3}=\dfrac{1}{4}-x\)
\(\Leftrightarrow\dfrac{4x-2}{3}=\dfrac{1-4x}{4}\)
\(\Rightarrow16x-8=3-12x\)
\(\Rightarrow x=\dfrac{11}{28}\)
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)
22 tháng 10 2017
a, \(\dfrac{1}{2}+\dfrac{2}{3}x=\dfrac{4}{5}\)
\(\Rightarrow\dfrac{2}{3}x=\dfrac{4}{5}-\dfrac{1}{2}\\ \Rightarrow\dfrac{2}{3}x=\dfrac{3}{10}\\ \Rightarrow x=\dfrac{3}{10}\cdot\dfrac{3}{2}\\ \Rightarrow x=\dfrac{9}{20}\)
b, \(x+\dfrac{1}{4}=\dfrac{4}{3}\)
\(\Rightarrow x=\dfrac{4}{3}-\dfrac{1}{4}\\ \Rightarrow x=\dfrac{13}{12}\)
c, \(\dfrac{3}{5}x-\dfrac{1}{2}=-\dfrac{1}{7}\)
\(\Rightarrow\dfrac{3}{5}x=-\dfrac{1}{7}-\dfrac{1}{2}\\ \Rightarrow\dfrac{3}{5}x=-\dfrac{9}{14}\\ \Rightarrow x=-\dfrac{9}{14}\cdot\dfrac{5}{3}\\ \Rightarrow x=\dfrac{15}{14}\)
d, \(\left|x-\dfrac{4}{5}\right|=\dfrac{3}{4}\)
\(\Rightarrow\left\{{}\begin{matrix}x-\dfrac{4}{5}=\dfrac{3}{4}\\x-\dfrac{4}{5}=-\dfrac{3}{4}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{3}{4}+\dfrac{4}{5}\\x=-\dfrac{3}{4}+\dfrac{4}{5}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{31}{20}\\x=\dfrac{1}{20}\end{matrix}\right.\)
e, \(lxl\) là j mk ko hiểu!
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 
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
\(\dfrac{5}{4}-\dfrac{1}{4}\left(x-\dfrac{2}{3}\right)=\dfrac{5}{2}\\ =>\dfrac{1}{4}\left(x-\dfrac{2}{3}\right)=\dfrac{5}{4}-\dfrac{5}{2}=-\dfrac{5}{4}\\ =>x-\dfrac{2}{3}=-\dfrac{5}{4}:\dfrac{1}{4}=-5\\ =>x=-5+\dfrac{2}{3}=-\dfrac{13}{3}\)