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**1. Homework Statement**

here's the picture and it's the second part of question 5:

http://imgur.com/ybSW4v4

**2. Homework Equations**

N/A

**3. The Attempt at a Solution**

so by intuition, I suspect that b = sup{a_n: n is in the natural numbers}

If we can show that, then it will follow from the first part of question 5 that what we are trying to prove does hold.

Ok well the problem is this. I'm given the definition of Least Upper Bound:

1) b is an upperbound

2) if y is an upperbound of the set, then (y > b) or (y = b).

I'm not sure how to prove 2) at all.. I need major help =/ Please..