=>\(x^2-2\cdot x-\left(3x-6\right)=0\)
=>\(x\cdot\left(x-2\right)-3\cdot\left(x-2\right)=0\)
=>\(\left(x-3\right)\cdot\left(x-2\right)=0\)
=> x=2 hoặc x=3
\(x^2-5x+6=0\)
\(\Leftrightarrow\) \(x^2-3x-2x+6>0\)
\(\Leftrightarrow\) \(x\left(x-3\right)-2\left(x-3\right)>0\)
\(\Leftrightarrow\) \(\left(x-3\right)\left(x-2\right)>0\)
\(\Leftrightarrow\) \(x>3\)
x^2-5x+6=0
<=> x^2-3x-2x+6=0
<=> x(x-3)-2(x-3)=0
<=> (x-3)(x-2)=0
<=> x-3=0 hoặc x-2=0
<=> x=3,x=2
S={3,2}