Giải
\(a,5-\left(x-2\right)^2=-4\\ =>\left(x-2\right)^2=5-\left(-4\right)\\ =>\left(x-2\right)^2=9\\ =>\left[{}\begin{matrix}\left(x-2\right)^2=3^2\\\left(x-2\right)^2=\left(-3\right)^2\end{matrix}\right.=>\left[{}\begin{matrix}x-2=3\\x-2=-3\end{matrix}\right.=>\left[{}\begin{matrix}x=5\\x=-1\end{matrix}\right.\)
Vậy \(x=5;x=-1\)