Ta có:
2m + 256 = 2n
=> 2n - 2m = 256
=> 2m.(2n-m - 1) = 256
Vì 2n-m - 1 chia 2 dư 1
=> \(\hept{\begin{cases}2^m=256=2^8\\2^{n-m}-1=1\end{cases}}\)=> \(\hept{\begin{cases}m=8\\2^{n-m}=2=2^1\end{cases}}\)=> \(\hept{\begin{cases}m=8\\n-m=1\end{cases}}\)=> \(\hept{\begin{cases}m=8\\n=9\end{cases}}\)