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Bài 2: 

a: =>x/4=1/8

hay x=1/2

b: \(\Leftrightarrow\dfrac{x}{-5}=\dfrac{11}{6}\)

hay x=-55/6

c: \(\Leftrightarrow\dfrac{-3.5}{x}=\dfrac{4.25}{8}\)

hay x=-112/17

29 tháng 8 2018

\(3\frac{1}{3}:x=2\frac{1}{2}:4\frac{5}{6}\)

\(\Rightarrow\frac{10}{3}:x=\frac{5}{2}:\frac{29}{6}\)

\(\Rightarrow\frac{10}{3}:x=\frac{15}{29}\)

\(\Rightarrow x=\frac{10}{3}:\frac{15}{29}\)

\(\Rightarrow x=\frac{58}{9}\)

25 tháng 9 2017

a) \(\frac{x}{7}=\frac{18}{14}\)

\(\frac{x}{7}=\frac{9}{7}\)

\(\Rightarrow x=9\)

b) \(6:x=1\frac{3}{4}:5\)

\(6:x=\frac{7}{4}.\frac{1}{5}\)

\(6:x=\frac{7}{20}\)

\(x=6:\frac{7}{20}\)

\(x=\frac{120}{7}\)

vay \(x=\frac{120}{7}\)

c) \(\frac{5,7}{0,35}=\frac{-x}{0,45}\)

\(\Rightarrow-0,35x=5,7.0,45\)

\(\Rightarrow-0,35x=2,565\)

\(\Rightarrow x=\frac{-2,565}{0,35}\)

\(\Rightarrow x=\frac{-513}{70}\)

vay \(x=\frac{-513}{70}\)

23 tháng 7 2016

\(\frac{1}{3}x:\frac{2}{3}=1\frac{3}{4}:\frac{2}{5}\)

\(\Rightarrow\frac{1}{3}x:\frac{2}{3}=\frac{35}{8}\)

\(\Rightarrow\frac{1}{3}x=\frac{35}{12}\)

\(\Rightarrow x=\frac{35}{4}\)

a) \(\left(\frac{1}{3}\cdot x\right):\frac{2}{3}=1\frac{3}{4}:\frac{2}{5}\)

\(=\left(\frac{1}{3}\cdot x\right):\frac{2}{3}=\frac{35}{8}\)

\(\Rightarrow\frac{1}{3}\cdot x=\frac{35}{8}\cdot\frac{2}{3}\)

\(\Rightarrow x=\frac{35}{12}:\frac{1}{3}=\frac{35}{4}\)

b) \(4,5:0,3=2,5:\left(0,1\cdot x\right)\)

\(=15=2,5:\left(0,1\cdot x\right)\)

\(\Rightarrow0,1\cdot x=2,25:15\)

\(\Rightarrow x=\frac{3}{20}:0,1=\frac{3}{2}=1,5\)

c) \(8:\left(\frac{1}{4}\cdot x\right)=2:0,02\)

\(8:\left(\frac{1}{4}\cdot x\right)=100\)

\(\Rightarrow\frac{1}{4}\cdot x=8:100\)

\(\Rightarrow x=\frac{2}{25}:\frac{1}{4}=\frac{8}{25}=0,32\)

d) \(3:2\frac{1}{4}=\frac{3}{4}:\left(6\cdot x\right)\)

\(=\frac{4}{3}=\frac{3}{4}:\left(6:x\right)\)

\(\Rightarrow6\cdot x=\frac{3}{4}:\frac{4}{3}\)

\(\Rightarrow x=\frac{9}{16}:6=\frac{3}{32}=0,09375\)

23 tháng 8 2021

a, \(\frac{x-6}{x+4}=\frac{2}{7}\Rightarrow7x-42=2x+8\)ĐK : \(x\ne-4\)

\(\Leftrightarrow5x=50\Leftrightarrow x=10\)(tm)

b, \(\left(x+5\right):2\frac{1}{2}=\frac{40}{x+5}\)ĐK : \(x\ne-5\)

\(\Leftrightarrow\frac{5\left(x+5\right)}{2}=\frac{40}{x+5}\Rightarrow5\left(x+5\right)^2=80\Leftrightarrow\left(x+5\right)^2=16\)

TH1 : \(x+5=4\Leftrightarrow x=-1\)

TH2 : \(x+5=-4\Leftrightarrow x=-9\)

15 tháng 10 2019

\(\frac{x-1}{x-2}=\frac{x+3}{x+4}\)

\(\Rightarrow\left(x-1\right)\left(x+4\right)=\left(x-2\right)\left(x+3\right)\)

\(\Leftrightarrow x^2+4x-x-4=x^2+3x-2x-6\)

\(\Leftrightarrow x^2+4x-x-4-x^2-3x+2x+6=0\)

\(\Leftrightarrow2x+2=0\)

\(\Leftrightarrow2x=-2\)

\(\Leftrightarrow x=-1\)VẬY X=-1 LÀ NGHIỆM CỦA PHƯƠNG TRÌNH \(\frac{x-1}{x-2}=\frac{x+3}{x+4}\)

15 tháng 10 2019

Ta có : \(\frac{x-1}{x-2}=\frac{x+3}{x+4}\)

\(\Rightarrow\left(x-1\right)\left(x+4\right)=\left(x-2\right)\left(x+3\right)\)

\(\Rightarrow x^2+4x-x-4=x^2+3x-2x-6\)

\(\Rightarrow3x-4=x+6\)

\(\Rightarrow3x-x=-4+6\)

\(\Rightarrow2x=-2\)

\(\Rightarrow x=-1\)

8 tháng 11 2018

\(\text{a)}\frac{37-x}{x+13}=\frac{3}{7}\)

\(\Leftrightarrow3\left(x+13\right)=7\left(37-x\right)\)

\(\Leftrightarrow3x+39=259-7x\)

\(\Leftrightarrow3x+7x=259-39\)

\(\Leftrightarrow10x=220\)

\(\Leftrightarrow x=22\)

8 tháng 11 2018

\(\text{b)}\frac{x+4}{20}=\frac{5}{x+4}\)

\(\Leftrightarrow\left(x+4\right)^2=100\)

\(\Leftrightarrow\orbr{\begin{cases}x+4=10\\x+4=-10\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=6\\x=-14\end{cases}}\)