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How to prove "v" is not a commutative operation?

Give the operation "v" on the integers such that: avb = a|a-b|

*those are absolute value symbols*

And V does not stand in for any standard operation, it just IS. How do you prove the operation is not communtative?

An explanation with steps would also be greatly appreciated =)

1 Answer

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  • 1 decade ago
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    An operation * is commutative on a set A iff a*b = b*a for every a,b ∊ A. That means we only need to find a single counterexample to prove that v isn't commutative. But that's easy

    -2v3 = -2|-2 - 3| = -2(5) = -10, and

    3v-2 = 3|3 -(-2)| = 3(5) = 15

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