I need to prove this question: 2 http://upload.wikimedia.org/math/9/b...cec0743fcd.png the set of all even natural numbers. Prove that 2 http://upload.wikimedia.org/math/9/b...cec0743fcd.png is countably infinite.

I know that I can combine each even number with an http://upload.wikimedia.org/math/9/b...cec0743fcd.png number so that 2=1, 4=2, 6=3,....

http://upload.wikimedia.org/math/9/b...cec0743fcd.png={1,2,3,4,5,6,.....,n} (n∈ http://upload.wikimedia.org/math/9/b...cec0743fcd.png)

2http://upload.wikimedia.org/math/9/b...cec0743fcd.png={2,4,6,8,10,12,...2n} (n∈ http://upload.wikimedia.org/math/9/b...cec0743fcd.png)

I know how to write it down but not how to prove it proper.

And ik know I need to prove its bijective but I dont know how.