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\(x^3-3x^2+3x-1\)
\(=x^3-3.x^2.1+3.x.1^2-1^3\)
\(=\left(x-1\right)^3\)
\(x^3-3x^2+3x-1\)
\(=x^3-3.x^2.1+3.x.1^2-1^3\)
\(=\left(x-1\right)^3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: =>-0,5x+1,5=0,4x-0,2
=>-0,9x=-1,7
=>x=17/9
3x-1/2x+3=3x+2/2x-1
=>6x^2-3x-2x+1=6x^2+4x+9x+6
=>-5x+1=13x+6
=>-8x=5
=>x=-5/8
b: \(\Leftrightarrow\left(4x-1\right)\left(-x+7\right)=\left(4x+5\right)\left(-x-2\right)\)
=>\(-4x^2+28x+x-7=-4x^2-8x-5x-10\)
=>29x-7=-13x-10
=>42x=-3
=>x=-1/14
c: =>7x=5y và 2x-y=15
=>7x-5y=0 và 2x-y=15
=>x=25; y=35
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{3x+2}{5x+7}=\dfrac{3x-1}{5x-3}\)
\(\Leftrightarrow\left(3x+2\right)\left(5x-3\right)=\left(5x+7\right)\left(3x-1\right)\)
\(\Leftrightarrow\left(3x+2\right)\left(5x-3\right)-\left(5x+7\right)\left(3x-1\right)=0\)
\(\Leftrightarrow\left(15x^2-9x+10x-6\right)-\left(15x^2-5x+21x-7\right)=0\)
\(\Leftrightarrow15x^2-9x+10x-6-15x^2+5x-21x+7=0\)
\(\Leftrightarrow-15x+1=0\)
\(\Leftrightarrow-15x=-1\)
\(\Leftrightarrow x=\dfrac{-1}{-15}=\dfrac{1}{15}\)
Vậy \(x=\dfrac{1}{15}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\dfrac{-1}{5}+\dfrac{3}{7}\right):\dfrac{2}{11}+\left(\dfrac{-4}{5}+\dfrac{4}{7}\right):\dfrac{2}{11}\)
\(=\dfrac{8}{35}:\dfrac{2}{11}+\dfrac{-8}{35}:\dfrac{2}{11}\)
\(=\dfrac{2}{11}:\left(\dfrac{8}{35}+\dfrac{-8}{35}\right)\)
\(=\dfrac{2}{11}:0=0\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{5}{7}+\dfrac{2}{3}x=\dfrac{3}{10}\)
\(\Rightarrow\dfrac{2}{3}x=\dfrac{3}{10}-\dfrac{5}{7}\)
\(\Rightarrow\dfrac{2}{3}x=-\dfrac{29}{70}\)
\(\Rightarrow x=-\dfrac{29}{70}:\dfrac{2}{3}\)
\(\Rightarrow x=-\dfrac{87}{140}\)