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a: =>2x>-6
hay x>-3
e: =>(5-x)/x<0
=>0<x<5
h: \(\Leftrightarrow\dfrac{x+5-x-3}{x+3}< 0\)
\(\Leftrightarrow x+3< 0\)
hay x<-3
g: \(\Leftrightarrow\dfrac{2x+7}{x+4}>0\)
\(\Leftrightarrow\left[{}\begin{matrix}x>-\dfrac{7}{2}\\x< -4\end{matrix}\right.\)
a) 1/4(x-3)+2=1/5
1/4.(x-3) = 1/5-2
1/4.(x-3) = -9/5
x-3 = (-9/5):1/4
x-3 = -36/5
x = -36/5+3
x= -21/5
a) 7x - 2x = 617 : 615 + 44
=> 5x = 36 + 44
=> 5x = 80
=> x = 80 : 5 = 16
b) 9x - 1 = 18 + 1/9 - 1/9 - 9
=> 9x - 1 = 9
=> x - 1 = 1
=> x = 1 + 1 = 2
c) [(6x - 39) : 7] . 4 = 12
=> (6x - 39) : 7 = 12 : 4
=> (6x - 39) : 7 = 3
=> 6x - 39 = 3.7
=> 6x - 39 = 21
=> 6x = 21 + 39
=> 6x = 60
=> x = 60 : 6
=> x = 10
d) 2 - (x - 1) - 3x = 20
=> 2 - x + 1 - 3x = 20
=> 3 - 4x = 20
=> 4x = 3 - 20
=> 4x = -17
=> x = -17 : 4 = -17/4
e) 2|x - 3| + 7 = 56 : 52
=> 2|x - 3| + 7 = 625
=> 2|x - 3| = 625 - 7
=> 2|x - 3| = 618
=> |x - 3| = 618 : 2
=> |x - 3| = 309
=> \(\orbr{\begin{cases}x-3=309\\x-3=-309\end{cases}}\)
=> \(\orbr{\begin{cases}x=312\\x=-306\end{cases}}\)
\(/x-\frac{1}{2}/=\frac{1}{3}\\ =>\orbr{\begin{cases}x-\frac{1}{2}=\frac{1}{3}\\x-\frac{1}{2}=-\frac{1}{3}\end{cases}}\\ =>\orbr{\begin{cases}x=\frac{1}{3}+\frac{1}{2}\\x=-\frac{1}{3}+\frac{1}{2}\end{cases}}\\ =>\orbr{\begin{cases}x=\frac{5}{6}\\x=\frac{1}{6}\end{cases}}\)
\(a,|x-\frac{1}{2}|=\frac{1}{3}\)
\(\Rightarrow\orbr{\begin{cases}x-\frac{1}{2}=\frac{1}{3}\\x-\frac{1}{2}=-\frac{1}{3}\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{5}{6}\\x=\frac{1}{6}\end{cases}}}\)
\(b,\frac{14}{15}:\frac{9}{10}=x:\frac{3}{7}\)
\(\frac{28}{27}=x:\frac{3}{7}\)
\(x=\frac{4}{9}\)
c: \(-\dfrac{1}{5}:\left(1\dfrac{2}{5}\right)=-\dfrac{2}{7}:x\)
=>\(-\dfrac{2}{7}:x=-\dfrac{1}{5}:\dfrac{7}{5}=\dfrac{-1}{5}\cdot\dfrac{5}{7}=-\dfrac{1}{7}\)
=>\(x=\dfrac{-2}{7}:\dfrac{-1}{7}=\dfrac{2}{7}\cdot\dfrac{7}{1}=2\)
d: \(1\dfrac{1}{2}:\dfrac{2}{3}=x:\dfrac{1}{9}\)
=>\(x:\dfrac{1}{9}=\dfrac{3}{2}\cdot\dfrac{3}{2}=\dfrac{9}{4}\)
=>\(x=\dfrac{9}{4}\cdot\dfrac{1}{9}=\dfrac{1}{4}\)
Em cảm ơn