# Math Help - Recursion (and sets)

1. ## Recursion (and sets)

I've been looking at this problem for ages and still can't work out what to do so help would be much appreciated!

Problem:
Set A is defined recursively. Find four elements in Set A.
2 ∈ A
x, y ∈ A, then x*y ∈ A (multiplication)

[I thought a clause may have been missing, but not entirely sure.. recursion isn't a strong point of mine..]

Thanks!

2. ## Re: Recursion (and sets)

Since 2 is in A, 2*2 = 4 must be in A. Since 4 and 2 are in A... can you take it from here?

3. ## Re: Recursion (and sets)

I didn't realise it was as easy as that.. Thank You!

Would the next one be 4*2 = 8 is in A?

yep