c: =>x^2-2x-3x+6=0
=>(x-2)(x-3)=0
=>x=2 hoặc x=3
b: =>|x-5|=16*7-89=112-89=23
=>x-5=23 hoặc x-5=-23
=>x=-18 hoặc x=28
a: \(\Leftrightarrow30x+5\left(x+8\right)-210=6\left(2x-2\right)+10\left(x-1\right)\)
=>30x+5x+40-210=12x-12+10x-10
=>35x-170=22x-22
=>13x=148
=>x=148/13
a) \(x+\dfrac{x+8}{6}-7=\dfrac{2x-2}{5}+\dfrac{x-1}{3}\)
\(\Leftrightarrow\dfrac{30\cdot x}{30}+\dfrac{5\cdot\left(x+8\right)}{30}-\dfrac{7\cdot30}{30}=\dfrac{6\cdot\left(2x-2\right)}{30}+\dfrac{10\left(x-1\right)}{30}\)
\(\Rightarrow30x+5\left(x+8\right)-7\cdot30=6\cdot\left(2x-2\right)+10\left(x-1\right)\)
\(\Leftrightarrow30x+5x+40-210=12x-12+10x-10\)
\(\Leftrightarrow35x-170=22x-22\)
\(\Leftrightarrow35x-22x=-22+170\)
\(\Leftrightarrow13x=148\)
\(\Leftrightarrow x=\dfrac{148}{13}\)
b) \(\left|x-5\right|=4^2\cdot7-89\)
\(\Leftrightarrow\left|x-5\right|=16\cdot7-89\)
\(\Leftrightarrow\left|x-5\right|=112-89\)
\(\Leftrightarrow\left|x-5\right|=23\)
TH1: \(\left|x-5\right|=\left|x-5\right|\) khi \(x-5\ge0\Leftrightarrow x\ge5\)
\(x-5=23\left(đk:x\ge5\right)\)
\(\Leftrightarrow x=23+5\)
\(\Leftrightarrow x=28\left(tm\right)\)
TH2: \(\left|x-5\right|=-\left(x-5\right)\) khi \(x-5< 0\Leftrightarrow x< 5\)
\(-\left(x-5\right)=23\left(đk:x< 5\right)\)
\(\Leftrightarrow x-5=-23\)
\(\Leftrightarrow x=-23+5\)
\(\Leftrightarrow x=-18\)
c) \(x^2-5x+6\)
\(\Leftrightarrow x^2-2x-3x+6=0\)
\(\Leftrightarrow\left(x^2-2x\right)-\left(3x-6\right)=0\)
\(\Leftrightarrow x\left(x-2\right)-3\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=3\end{matrix}\right.\)
