How can I put A={1,4,7,10,13,16,19,22,25,28} in set builder notation. I just learned this and can't figure it out.

Answer 1

notice all the numbers are 3 apart

so the formula to generate the numbers would be
3n - 2, where n ∈ N₀

so

A = { 3n-2 | n ∈ N₀ , n ≤ 10 }

Answer 2

I just noticed that I wanted the n's to start at 1, not at 0
so change it to

{......| n ∈ N ......}