# Union and addition of Intervals

• Jan 30th 2013, 12:02 PM
willywonk
A=[-1,0)
B=(0,1]

Find A U B and A + B (x+y such that x is an element of A and y is an element of B)

I know how to find the answers of two closed intervals but I'm not sure about intervals that are open and closed. Would the answers be considered compact?

Thanks
• Jan 30th 2013, 12:22 PM
Plato
Re: Union and addition of Intervals
Quote:

Originally Posted by willywonk
A=[-1,0) , B=(0,1]
Find A U B and A + B (x+y such that x is an element of A and y is an element of B)

I know how to find the answers of two closed intervals but I'm not sure about intervals that are open and closed. Would the answers be considered compact?

I am not sure exactly notation you are required to use.

$A\cup B=[-1,1]\setminus\{0\}$. WHY?

Edit: I don't understand what happened but part of my reply is missing.

$A+B=(-1,1)$. But you must explain why.
• Jan 30th 2013, 02:38 PM
HallsofIvy
Re: Union and addition of Intervals
I don't know about the answers being compact but the sets are not.