Why does $2^{n+1} + 2^{n+1} = 2^{n+2}$? Simple question, why does:
$2^{n+1} + 2^{n+1} = 2^{n+2}$ ?
Furthermore, why does this only work for powers of 2?
Thanks.

Note that $2^{n+1}=2\cdot 2^n=2^n+2^n$
If you try it with $3$ you get $3^{n+1}=3\cdot 3^n=3^n+3^n+3^n$
