16.4^(x+2)-16, 2^(x+1)+1=0

Not sure what to do with that comma:

4^(x+2)-16, 2^(x+1)+1=0

clearly 2^(x+1)+1=0 has no solutions, since 2^(x+1) is always positive.

Maybe you can clarify just what it is you have, and what it is you want...