Question

Prove that 2n > n for all positive integers n.

Answer 1

let n be 1 
so,2(1)<1
2<1

Answer 2

If n is positive
 n>0
To prove 2n>n (+ve)
Let's  assume that it's not the case
 Therefore,
2n < n
2n-n < n-n
n <0
Which is a contradiction 
Hence 2n>n for positive reals