# Examples of partitions

#### ver_mathstats

1. The problem statement, all variables and given/known data
Show an example of a partition of the nonzero integers into two infinite sets. Show an example of a partition of the nonzero integers into infinitely many sets, such that each set of the partition contains exactly two elements.

2. Relevant equations

3. The attempt at a solution
I know that a partition A is a collection of subsets {Ai}.

An example of a partition of the nonzero integers into two infinite sets would be A1={k∈ℤ: 2k, k≠0} and A2={m∈ℤ:2m+1, m≠0}, so that would mean ℙ={A1, A2}. Am I on the write track with this? I assume since ever number is either odd or even then I could write two sets with even and odd numbers that are infinite but do not include 0.

I am confused how to give an example for the second part however?

Thank you.

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#### PeroK

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I am confused how to give an example for the second part however?

Thank you.
No ideas at all?

What about partitioning the set $\{-3, -2, -1, 1, 2, 3 \}$ into subsets, each with two members? Could you do that?

#### ver_mathstats

No ideas at all?

What about partitioning the set $\{-3, -2, -1, 1, 2, 3 \}$ into subsets, each with two members? Could you do that?
Oh okay that would make sense, I think the fact it was infinite is what threw me off. So we would just do Aj={-j.j}? Thank you for the reply.

#### LCKurtz

Homework Helper
Gold Member
1. The problem statement, all variables and given/known data
Show an example of a partition of the nonzero integers into two infinite sets. Show an example of a partition of the nonzero integers into infinitely many sets, such that each set of the partition contains exactly two elements.

2. Relevant equations

3. The attempt at a solution
I know that a partition A is a collection of subsets {Ai}.
There is more to it than that though. It isn't just any old collection of subsets.

An example of a partition of the nonzero integers into two infinite sets would be A1={k∈ℤ: 2k, k≠0} and A2={m∈ℤ:2m+1, m≠0}, so that would mean ℙ={A1, A2}. Am I on the write track with this? I assume since ever number is either odd or even then I could write two sets with even and odd numbers that are infinite but do not include 0.
What you have given is not a partition. You don't have $1$ in either subset.

#### ver_mathstats

There is more to it than that though. It isn't just any old collection of subsets.

What you have given is not a partition. You don't have $1$ in either subset.
Oh okay, sorry, I still am new to what partitions are. A1={xεZ:x>0} and A2={xεZ:x<0}, for every x∈Z* so P={A1, A2}? Thank you for the reply.

#### LCKurtz

Homework Helper
Gold Member
Oh okay, sorry, I still am new to what partitions are. A1={xεZ:x>0} and A2={xεZ:x<0}, for every x∈Z* so P={A1, A2}? Thank you for the reply.
Are you asking us or telling us? What are the properties of a partition? Do your $A_1$ and $A_2$ satisfy those properties?

"Examples of partitions"

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