I have the following question,
Relation on the reals: $x\thicksim y$ means that $xy \geq 0$, and I have to decide whether or not it is an equivalence relation.
First, I know that it is reflexive since I just can take any positive or negative real number and I'll get: $xy \geq 0$.
Deciding whether it is symmetric, I know that if it is, then $x\thicksim y$ and $y \thicksim x $. But if it's not, then $x\thicksim y$ BUT $y \not\thicksim x$.
If I wanted to do a counterexample to show that it is not symmetric, can I just take any number x and -y? (Although I know that will mean that $x \not\thicksim y $ and $y \not\thicksim x$). I have the same problems to show if it's transitive.
Thanks in advance!
Best Answer
0 ~ -1
0 ~ 1
but not -1 ~ 1
It is not an equivalence relation