a) \(\sqrt{x^2-x-4}=\sqrt{x-1}\)
\(x^2-x-4=x-1\)
\(x^2-x-4-x+1=0\)
\(x^2-2x-5=0\)
\(\left(x^2-2.x.1+1^2\right)-6=0\)
\(\left(x-1\right)^2=6\)
⇒\(\left\{{}\begin{matrix}x-1=6\\x-1=-6\end{matrix}\right.\) ⇒\(\left\{{}\begin{matrix}x=7\\x=-5\end{matrix}\right.\)