- #1
utstatistics
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Homework Statement
If S1, S2 are nonempty subsets of ℝ that are bounded from above, prove that
l.u.b. {x+y : x \in S1, y \in S2 } = l.u.b. S1 + l.u.b. S2
Homework Equations
Least Upper Bound Property
The Attempt at a Solution
Using the least upper bound property, let us suppose that a is an upper bound for S1 and b is an upper bound for S2, as they are both a set of real numbers. Then there exists an x in S1 s.t. x≤a and there exists a y in S2 s.t. y≤b. By adding them together, x+y≤a+b where a and b are the upper bounds for their respected set of real numbers. Thus, it is equal to l.u.b. S1 + l.u.b. S2
I think this is how it goes. I'm sorry if my proof is horrible; it has been a significant period of time since I've done proofs, as statistics and probability classes don't use proofs! Also, I can't get \in to work. Sorry about that!