How do you do these questions?
5. The set {-1,0,1} is closed under which of these operations?
A-Addition S-Subtraction M-Multiplication D-Division
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District 2 2012
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District 2 2012
by hydreichomp » Mon Mar 18, 2013 10:05 pm
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Re: District 2 2012
by Fredfredburger » Tue Mar 19, 2013 12:18 am
Here's the wikipedia page.
Basically if you do a binary operation on the set and are left with an element of said set every time, then that set is closed. Here 1+1=2(you can use the same element twice), so addition isn't closed. -1-1=-2, so subtraction isn't closed. Multiplication will give only -1,1, or 0, so that is closed. Division is open since you can't divide by 0.
Multiplication is your answer.
Basically if you do a binary operation on the set and are left with an element of said set every time, then that set is closed. Here 1+1=2(you can use the same element twice), so addition isn't closed. -1-1=-2, so subtraction isn't closed. Multiplication will give only -1,1, or 0, so that is closed. Division is open since you can't divide by 0.
Multiplication is your answer.
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