a) 5n=625
=> 5n=54
=> n=4
b) 12n=144
=> 12n=122
=> n=2
c) (n-2)2=(n-2)4
=> (n-2)2-(n-2)4=0
=> (n-2)2[1-(n-2)2]=0
=> \(\left[{}\begin{matrix}\left(n-2\right)^2=0\\1-\left(n-2\right)^2=0\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}n-2=0\Rightarrow n=2\\\left(n-2\right)^2=1\Rightarrow n-2=\pm1\Rightarrow\left[{}\begin{matrix}n-2=1\Rightarrow n=3\-2=-1\Rightarrow n=1\end{matrix}\right.\end{matrix}\right.\)
vay n\(\in\) { 1;2;3}
=>
