# Sets

• Oct 15th 2008, 04:54 PM
dolphinlover
Sets
I'm not real sure about a defn. in this problem and need some clarification.
"The universe is all Real #'s. Let A be the closed interval [0,2] and let B be the closed interval [-1,1]. Find A\B, etc etc."

My question is this: By closed interval, does this mean (for A) that the set is all real #'s between (and including) zero and two? And if not, what does it mean?

Thanx!
• Oct 15th 2008, 04:58 PM
terr13
[ denotes closed, as in it contains the number, in this case 0 and 2
( denotes open, contains everything up to the number but not the number itself.
• Oct 15th 2008, 08:01 PM
dolphinlover
Quote:

Originally Posted by terr13
[ denotes closed, as in it contains the number, in this case 0 and 2
( denotes open, contains everything up to the number but not the number itself.

So...Just as I thought....The set contains every real # between and including 0 & 2 for set A; and -1 & 1 for set B...correct? Or just A={0,2} and B={-1,1}....doesn't seem right...
• Oct 15th 2008, 08:02 PM
terr13
All reals in between and including.
• Oct 15th 2008, 08:08 PM
dolphinlover
Quote:

Originally Posted by terr13
All reals in between and including.

Just as I thought..Thank You!