1. partition help

if set A = {3,4,5}
P(A) = {{},{3},{4},{5},{3,4},{3,5},{4,5},{3,4,5}}

A partition of A with 3 elements is
is A1 = {3,4,5} when A2 is an empty set

am I on the right track?
Thanks for any Input.

2. Originally Posted by dunsta
if set A = {3,4,5}
P(A) = {{},{3},{4},{5},{3,4},{3,5},{4,5},{3,4,5}}
A partition of A with 3 elements is is A1 = {3,4,5} when A2 is an empty set
In partition, no cell can be empty. So no that is not a partition.
However, $A_1=\{3,4,5\}$ is a trivial one cell partition.