\(\Leftrightarrow x^2-x-6=0\)
\(\Leftrightarrow x^2+x-6x-6=0\)
\(\Leftrightarrow x\left(x+1\right)-6\left(x+1\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=6\end{matrix}\right.\)
`x^2 - 6 = x`
`<=> x^2 - x - 6 = 0`
`<=> x^2 + x - 6x - 6 = 0`
`<=> x(x + 1) - 6(x + 1) = 0`
`<=> (x + 1)(x + 6) = 0`
`<=>` `+)` `x + 1 = 0 => x = -1`
`<=>` `+)` `x - 6 = 0 => x = 6`
\(x^2-6=x\)
\(\Leftrightarrow x^2-x-6=0\)
\(\Leftrightarrow x^2+2x-3x-6=0\)
\(\Leftrightarrow x\left(x+2\right)-3\left(x+2\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+2=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)
\(S=\left\{3;-2\right\}\)