\(\left(x-1\right)\left(x+1\right)-3x-6=6\)
\(x^2-1^2-3x-6-6=0\)
\(x^2-1-3x-12=0\)
\(x^2-3x-13=0\)
\(\orbr{\begin{cases}x=\frac{3-\sqrt{61}}{2}\\x=\frac{3+\sqrt{61}}{2}\end{cases}}\)
\(\left(x-1\right)\left(x+1\right)-3x-6=6\)
\(\left(x-1\right)\left(x+1\right)-3x=12\)
\(\left(x-1\right)x-\left(x-1\right)1-\left(1+2\right)x=12\)
\(\left(x-1-1+2\right)x-x-1=12\)
\(\left(x-1-1+2-1\right)x=11\)
\(\left(x-1\right)x=11\)
\(x^2-x=11\)
Đk : x > 4
\(x=4\Rightarrow16-4=11\left(\varnothing\right)\)
\(x\in\varnothing\)
