How does this composite function simplify to 2(2^x) ?

[lioric]

f(x)=2xand g(x)=2^x
Find the composite function of fg(x)
fg(x)
=f(g(x))
=f(2^x)
=2(2^x)

I don’t understand how this in turn equals to 2^(x+1)

[Moderator's note: Moved from a technical forum and thus no template.]

 

[fresh_42]

How is $2^n$ defined?

 

[lioric]

Never mind I got it
2^1 x 2^x = 2^(x+1)

 

[lioric]

Thank you anyway