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4 tháng 3 2022

ĐKXĐ:\(\left\{{}\begin{matrix}x\ne0\\x\ne-3\end{matrix}\right.\)

\(\dfrac{80}{x}-\dfrac{80}{x+3}=\dfrac{3}{20}\\ \Leftrightarrow80\left(\dfrac{1}{x}-\dfrac{1}{x+3}\right)=\dfrac{3}{20}\\ \Leftrightarrow\dfrac{x+3-x}{x\left(x+3\right)}=\dfrac{3}{1600}\\ \Leftrightarrow\dfrac{3}{x^2+3x}=\dfrac{3}{1600}\\ \Leftrightarrow3x^2+9x=4800\\ \Leftrightarrow x^2+3x-1600=0\\\)

Nghiệm xấu lắm bạn

11 tháng 7 2017

giúp zới

khocroi

17 tháng 4 2022

Quy đồng

tính 1 cách thuận tiện

=)

4 tháng 3 2022

\(a,\dfrac{3}{4}x-\dfrac{7}{12}=\dfrac{5}{6}-\dfrac{2}{3}\\ \Rightarrow\dfrac{3}{4}x-\dfrac{7}{12}=\dfrac{1}{6}\\ \Rightarrow\dfrac{3}{4}x=\dfrac{1}{6}+\dfrac{7}{12}\\ \Rightarrow\dfrac{3}{4}x=\dfrac{3}{4}\\ \Rightarrow x=\dfrac{3}{4}:\dfrac{3}{4}\\ \Rightarrow x=1\\ b,\dfrac{-5}{x}=\dfrac{20}{28}\\ \Rightarrow\dfrac{-5}{x}=\dfrac{5}{7}\\ \Rightarrow\dfrac{-5}{x}=\dfrac{-5}{-7}\\ \Rightarrow x=-7\\ c,2\dfrac{1}{3}:x=7\\ \Rightarrow\dfrac{7}{3}:x=7\\ \Rightarrow x=\dfrac{7}{3}:7\\ \Rightarrow x=\dfrac{1}{3}\)

\(d,\dfrac{-105}{12}< x< \dfrac{20}{7}\Rightarrow x\in\left\{-8;-7;...;2\right\}\)

a: \(\Leftrightarrow x\cdot\dfrac{3}{4}=\dfrac{3}{4}\)

hay x=1

b: \(\Leftrightarrow x=\dfrac{-28\cdot5}{20}=-7\)

c: \(\Leftrightarrow x=\dfrac{7}{3}:7=\dfrac{1}{3}\)

d: \(\Leftrightarrow-8< x< 3\)

hay \(x\in\left\{-7;-6;-5;-4;-3;-2;-1;0;1;2\right\}\)

6 tháng 5 2017

a) Vì \(\dfrac{x+5}{3}\)= \(\dfrac{x-6}{7}\) nên 7(x+5) = 3(x-6)

=> 7x+ 35 = 3x - 18

7x - 3x = -18 -35

4x = -53

x = -53:4

x = \(\dfrac{-53}{4}\)

8 tháng 6 2021

\(y\dfrac{5}{y}=\dfrac{86}{y}\)

\(\Leftrightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\left(y\ne0\right)\)

\(\Leftrightarrow y^2+5=86\)

\(\Leftrightarrow y^2=81\)

\(\Leftrightarrow y=\pm9\)

8 tháng 6 2021

\(y\dfrac{5}{y}=\dfrac{86}{y}\\ \Rightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\\ \Rightarrow y^2+5=86\\ \Rightarrow y^2=81\\ \Rightarrow\left[{}\begin{matrix}y=9\\y=-9\end{matrix}\right.\)

Vậy \(y\in\left\{-9;9\right\}\)

25 tháng 3 2023

a, \(x\cdot\dfrac{-5}{8}=\dfrac{15}{32}\)

\(x=\dfrac{15}{32}:\dfrac{-5}{8}\)

\(x=\dfrac{-3}{4}\)

 

b, \(\dfrac{3}{10}:x=\dfrac{-9}{20}\)

\(x=\dfrac{3}{10}:\dfrac{-9}{20}\)

\(x=-\dfrac{2}{3}\)

 

c, \(\dfrac{-1}{4}x+\dfrac{4}{5}=\dfrac{3}{4}\)

\(\dfrac{-1}{4}x=\dfrac{3}{4}-\dfrac{4}{5}\)

\(\dfrac{-1}{4}x=-\dfrac{1}{20}\)

\(x=-\dfrac{1}{20}:\dfrac{-1}{4}\)

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

 

d, \(\dfrac{-7}{8}+\dfrac{2}{3}:x=\dfrac{3}{5}\cdot\dfrac{-5}{12}\)

\(\dfrac{-7}{8}+\dfrac{2}{3}:x=-\dfrac{1}{4}\)

\(\dfrac{2}{3}:x=-\dfrac{1}{4}+\dfrac{-7}{8}\)

\(\dfrac{2}{3}:x=\dfrac{5}{8}\)

\(x=\dfrac{2}{3}:\dfrac{5}{8}\)

\(x=\dfrac{16}{15}\)

 

 

 

#YVA6

25 tháng 3 2023

\(a,x.\dfrac{-5}{8}=\dfrac{15}{32}\)

\(\Leftrightarrow x=\dfrac{15}{32}:\dfrac{-5}{8}\)

\(\Leftrightarrow x=\dfrac{15}{32}.\dfrac{-8}{5}\)

\(\Leftrightarrow x=-\dfrac{3}{4}\)

\(b,\dfrac{3}{10}:x=-\dfrac{9}{20}\)

\(\Leftrightarrow x=\dfrac{3}{10}:\dfrac{-9}{20}\)

\(\Leftrightarrow x=\dfrac{3}{10}.\dfrac{-20}{9}\)

\(\Leftrightarrow x=-\dfrac{2}{3}\)

\(c,-\dfrac{1}{4}x+\dfrac{4}{5}=\dfrac{3}{4}\)

\(\Leftrightarrow-\dfrac{1}{4}x=\dfrac{3}{4}-\dfrac{4}{5}\)

\(\Leftrightarrow-\dfrac{1}{4}x=-\dfrac{1}{20}\)

\(\Leftrightarrow x=-\dfrac{1}{20}\times\left(-4\right)\)

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

\(d,-\dfrac{7}{8}+\dfrac{2}{3}:x=\dfrac{3}{5}.\dfrac{-5}{12}\)

\(\Leftrightarrow-\dfrac{7}{8}+\dfrac{2}{3}:x=-\dfrac{1}{4}\)

\(\Leftrightarrow\dfrac{2}{3}:x=-\dfrac{1}{4}+\dfrac{7}{8}\)

\(\Leftrightarrow\dfrac{2}{3}:x=\dfrac{5}{8}\)

\(\Leftrightarrow x=\dfrac{2}{3}:\dfrac{5}{8}\)

\(\Leftrightarrow x=\dfrac{16}{15}\)

11 tháng 3 2022

a, \(\left(\dfrac{7}{2}-2x\right).\dfrac{10}{3}=\dfrac{22}{3}\Leftrightarrow\dfrac{7}{2}-2x=\dfrac{22}{10}=\dfrac{11}{5}\)

\(\Leftrightarrow2x=\dfrac{13}{10}\Leftrightarrow x=\dfrac{13}{20}\)

b, \(\dfrac{4x}{9}=\dfrac{9}{8}-\dfrac{125}{1000}=1\Leftrightarrow x=\dfrac{9}{4}\)

c, \(-\dfrac{x}{21}=\dfrac{60}{21}\Rightarrow x=-60\)

27 tháng 9 2023

\(a,x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{\left(-1\right)}{3}\)

\(x+\dfrac{1}{3}=\dfrac{2}{5}+\dfrac{1}{3}\)

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

\(x=\dfrac{2}{5}\)

\(---\)

\(b,\dfrac{5}{8}-x=\dfrac{-3}{20}-\dfrac{\left(-1\right)}{6}\)

\(\dfrac{5}{8}-x=\dfrac{-3}{20}+\dfrac{1}{6}\)

\(\dfrac{5}{8}-x=\dfrac{-9}{60}+\dfrac{10}{60}\)

\(\dfrac{5}{8}-x=\dfrac{1}{60}\)

\(x=\dfrac{5}{8}-\dfrac{1}{60}\)

\(x=\dfrac{75}{120}-\dfrac{2}{120}\)

\(x=\dfrac{73}{120}\)

#\(Toru\)

a: x+2/5=1/2

=>x=1/2-2/5=5/10-4/10=1/10

b; x-2/5=2/7

=>x=2/7+2/5=10/35+14/35=24/35

c: 3/5-x=1/10

=>x=3/5-1/10=6/10-1/10=5/10=1/2

d: x*3/4=9/20

=>x=9/20:3/4=9/20*4/3=36/60=3/5

e: x:1/7=14

=>x=14*1/7=2

f: =>x+1/4=2/5:1/2=4/5

=>x=4/5-1/4=16/20-5/20=11/20

g: =>x*2/3=9/12+2/3=3/4+2/3=9/12+8/12=17/12

=>x=17/12:2/3=17/12*3/2=51/24=17/8