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13 tháng 3 2020
a) Ta có:
\(\frac{3}{x+2}=\frac{5}{2x+1}\)
\(\Rightarrow3\left(2x+1\right)=5\left(x+2\right)\)
\(\Rightarrow6x+3=5x+10\)
\(\Rightarrow6x-5x=10-3\)
\(\Rightarrow x=7\)
b)Ta có:
\(\frac{5}{8x-2}=\frac{-4}{7-x}\)
\(\Rightarrow5\left(7-x\right)=-4\left(8x-2\right)\)
\(\Rightarrow35-5x=-32x+8\)
\(\Rightarrow-5x+32x=8-35\)
\(\Rightarrow27x=-27\)
\(\Rightarrow x=-1\)
c) Ta có:
\(\frac{4}{3}=\frac{2x-1}{x}\)
\(\Rightarrow4x=3\left(2x-1\right)\)
\(\Rightarrow4x=6x-3\)
\(\Rightarrow3=6x-4x=2x\)
\(\Rightarrow x=\frac{3}{2}\)
13 tháng 3 2020
d)Ta có:
\(\frac{2x-1}{3}=\frac{3x+1}{4}\)
\(\Rightarrow4\left(2x-1\right)=3\left(3x+1\right)\)
\(\Rightarrow8x-4=9x+3\)
\(\Rightarrow8x-9x=3+4\)
\(\Rightarrow-x=7\Rightarrow x=-7\)
e)Ta có:
\(\frac{4}{x+2}=\frac{7}{3x+1}\)
\(\Rightarrow4\left(3x+1\right)=7\left(x+2\right)\)
\(\Rightarrow12x+4=7x+14\)
\(\Rightarrow12x-7x=14-4\)
\(\Rightarrow5x=10\)
\(\Rightarrow x=2\)
f)Ta có:
\(\frac{-3}{x+1}=\frac{4}{2-2x}\)
\(\Rightarrow-3\left(2-2x\right)=4\left(x+1\right)\)
\(\Rightarrow-6+6x=4x+4\)
\(\Rightarrow6x-4x=4+6\)
\(\Rightarrow2x=10\)
\(\Rightarrow x=5\)
NC
27 tháng 8 2020
a) Ta có: \(-x+\frac{4}{7}=\frac{1}{3}\)
\(\Leftrightarrow-x=-\frac{5}{21}\)
\(\Rightarrow x=\frac{5}{21}\)
b) Ta có: \(x\div\left(-\frac{1}{3}\right)^2=-\frac{1}{3}\)
\(\Rightarrow x=\left(-\frac{1}{3}\right)^3=-\frac{1}{27}\)
c) \(\left(\frac{3}{5}\right)^5.x=\left(\frac{3}{5}\right)^7\)
\(\Rightarrow x=\left(\frac{3}{5}\right)^2=\frac{9}{25}\)
27 tháng 8 2020
\(a.-x+\frac{4}{7}=\frac{1}{3}\)
\(-x=\frac{1}{3}-\frac{4}{7} \)
\(-x=\frac{7}{21}-\frac{12}{21}\)
\(-x=\frac{-5}{21}\)
\(x=\frac{5}{21}\)
\(b.x:\left(\frac{-1}{3}\right)^2=\frac{-1}{3}\)
\(x=\frac{-1}{3}.\left(\frac{-1}{3}\right)^2\)
\(x=\frac{-1}{3}.\frac{-1}{3}.\frac{-1}{3}\)
\(x=\frac{-1}{27}\)
\(c.\left(\frac{3}{5}\right)^5.x=\left(\frac{3}{5}\right)^7\)
\(x=\left(\frac{3}{5}\right)^7:\left(\frac{3}{5}\right)^5\)
\(x=\left(\frac{3}{5}\right)^2\)
\(x=\frac{3}{5}.\frac{3}{5}\)
\(x=\frac{9}{25}\)
S
20 tháng 7 2019
\(a,\frac{3}{7}+\left|2x-\frac{1}{2}\right|=\frac{4}{5}\)
\(\Rightarrow\left|2x-\frac{1}{2}\right|=\frac{13}{35}\)
\(\Rightarrow2x-\frac{1}{2}=\pm\left(\frac{13}{35}\right)\)
\(\Rightarrow\orbr{\begin{cases}2x-\frac{1}{2}=\frac{13}{35}\\2x-\frac{1}{2}=\frac{-13}{35}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x=\frac{61}{70}\\2x=\frac{9}{70}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{61}{140}\\x=\frac{9}{140}\end{cases}}\)
~Study well~
#KSJ
S
20 tháng 7 2019
\(b,\frac{3}{4}-4\times\left|2x+1\right|=\frac{1}{2}\)
\(\Rightarrow4\times\left|2x+1\right|=\frac{1}{4}\)
\(\Rightarrow\left|2x+1\right|=\frac{1}{16}\)
\(\Rightarrow2x+1=\pm\left(\frac{1}{16}\right)\)
\(\Rightarrow\orbr{\begin{cases}2x+1=\frac{1}{16}\\2x+1=\frac{-1}{16}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x=\frac{-15}{16}\\2x=\frac{-17}{16}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{-15}{32}\\x=\frac{-17}{32}\end{cases}}\)
~Study well~
#KSJ
F
Tim x biet
a) x - \(\frac{5}{7}\)=\(\frac{1}{9}\)
b)\(\frac{-3}{7}\)- x = \(\frac{4}{5}+\frac{-2}{3}\)
3
26 tháng 5 2020
\(x-\frac{5}{7}=\frac{1}{9}\)
\(x=\frac{52}{63}\)
\(\frac{-3}{7}-x=\frac{4}{5}+\frac{-2}{3}\)
\(\frac{-3}{7}-x=\frac{2}{15}\)
\(x=\frac{-59}{105}\)
7 tháng 5 2020
a, \(\frac{3}{7}=-\frac{x}{21}\Leftrightarrow63=-7x\Leftrightarrow x=-9\)
b, \(\frac{x-1}{6}=\frac{2}{3}\Leftrightarrow\frac{x-1}{6}=\frac{4}{6}\Leftrightarrow x-1=4\Leftrightarrow x=5\)
c, \(\frac{-15}{2x+3}=\frac{-5}{8}\Leftrightarrow-120=-10x-15\Leftrightarrow-10x=-105\Leftrightarrow x=10,5\)( chưa xem lại ko chắc , thử lại giúp mk nha )
7 tháng 5 2020
a) \(\frac{3}{7}=\frac{-x}{21}\)
\(\Rightarrow-7x=21.3\)
\(-7x=63\)
\(x=63:\left(-7\right)\)
\(x=-9\)
Vậy x=-9
b) \(\frac{x-1}{6}=\frac{2}{3}\)
\(\Rightarrow\left(x-1\right).3=6.2\)
\(3x-3=12\)
\(3x=12+3\)
\(3x=15\)
\(x=15:3\)
\(x=5\)
Vậy x=5
PH
2
7 tháng 5 2020
a, \(\frac{x-1}{9}=\frac{8}{3}\Leftrightarrow\frac{x-1}{9}=\frac{24}{9}\Leftrightarrow x-1=24\Leftrightarrow x=25\)
b, \(\frac{x+2}{3}=\frac{2x-1}{5}\Leftrightarrow\frac{5x+10}{15}=\frac{6x-3}{15}\Leftrightarrow5x+10=6x-3\)
\(\Leftrightarrow5x+10-6x+3=0\Leftrightarrow-x+13=0\Leftrightarrow x=13\)
7 tháng 5 2020
a) \(\frac{x-1}{9}=\frac{8}{3}\)
\(\Leftrightarrow3\left(x-1\right)=8.9\)
\(\Leftrightarrow3x-3=72\)
\(\Leftrightarrow3x=75\)
\(\Leftrightarrow x=25\)
b) \(\frac{x+2}{3}=\frac{2x-1}{5}\)
\(\Leftrightarrow5\left(x+2\right)=3\left(2x-1\right)\)
\(\Leftrightarrow5x+10=6x-3\)
\(\Leftrightarrow5x-6x=-3-10\)
\(\Leftrightarrow-x=-13\)
\(\Leftrightarrow x=13\)
\(x\div4\frac{1}{3}=-2,5\)
=> \(x\div\frac{13}{3}=\frac{-5}{2}\)
=> \(x=\frac{-65}{6}\)
\(7-\left|2x-1\right|=2\)
=> \(\left|2x-1\right|=5\)
=> \(\orbr{\begin{cases}2x-1=5\\2x-1=-5\end{cases}\Rightarrow\orbr{\begin{cases}2x=6\\2x=-4\end{cases}\Rightarrow}\orbr{\begin{cases}x=3\\x=-2\end{cases}}}\)
f, \(x:4\frac{1}{3}=-2,5\)
\(\Leftrightarrow x:\frac{13}{3}=-2,5\Leftrightarrow x=-2,5.\frac{13}{3}=-\frac{65}{6}\)
g, \(7-\left|2x-1\right|=2\)
\(\Leftrightarrow\left|2x-1\right|=5\)
\(\Leftrightarrow\orbr{\begin{cases}2x-1=5\\2x-1=-5\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=6\\2x=-4\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=3\\x=-2\end{cases}}}\)