\(Fe_3O_4+8HCl--->FeCl_2+2FeCl_3+4H_2O\)

\(NaOH+HCl--->NaCl+H_2O\)

\(Zn\left(OH\right)_2+2HCl--->ZnCl_2+2H_2O\)

\(Mg+2HCl--->MgCl_2+H_2\uparrow\)

\(2Al+6HCl--->2AlCl_3+3H_2\uparrow\)

\(\left(x-2\right)\left(x^2-25\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x^2-25=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\pm5\end{matrix}\right.\)