Let $A$ be a nonempty set. Prove that if $f$ maps $\>P (A)$ to $A$ then $f$ is not one-to-one.
Related Topics: Pigeonhole Principle
Let $A$ be a nonempty set. Prove that if $f$ maps $\>P (A)$ to $A$ then $f$ is not one-to-one.
Related Topics: Pigeonhole Principle