# can someone possibly explain the following lemma?

• Oct 17th 2010, 08:02 AM
tn11631
can someone possibly explain the following lemma?
While reviewing my text book I came across a lemma that I just can't seem to wrap my head around no matter how I try to break it down. I was wondering if someone had an esier way of explaining it. The lemma is as follows:

Let n be a positive integer. Let A be a set; let a $_0$ be an element of A. Then there exists a bijective correspondence f on the set A with the set {1,...,n+1} if and only if there exists a bijective correspondence g of the set A-{a $_0$} with the set {1,...,n}.

I know bijective correspondence we want one to one AND onto and I also have the proof sitting in front of me (if one wishes me to post it I will) but I feel when I fully understand the lemma the proof will follow easily. For some reason as many times as I read it, it seems to be going over my head.
• Oct 17th 2010, 08:19 AM
Mauritzvdworm
Say you have a set A which "contains" n+1 elements, now if you remove one of those elements then the remaining set should "contain" only n elements
• Oct 17th 2010, 08:29 AM
tn11631
Lol thank you! I wish they can just sometimes state it plainly lol thank u tho!