1. Let A and B be two finite sets. Justify the following statements. (a) If f: A B is an injection, then |A|≤|B|. (Consider the Pigeonhole Principle.) (b) If f: AB is a surjection, then there is an injection g: BA, and deduce from the first part that B|≤|A|.

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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1. Let \( A \) and \( B \) be two finite sets. Justify the following statements.

(a) If \( f: A \rightarrow B \) is an injection, then \( |A| \leq |B| \). (Consider the Pigeonhole Principle.)

(b) If \( f: A \rightarrow B \) is a surjection, then there is an injection \( g: B \rightarrow A \), and deduce from the first part that \( |B| \leq |A| \).
Transcribed Image Text:1. Let \( A \) and \( B \) be two finite sets. Justify the following statements. (a) If \( f: A \rightarrow B \) is an injection, then \( |A| \leq |B| \). (Consider the Pigeonhole Principle.) (b) If \( f: A \rightarrow B \) is a surjection, then there is an injection \( g: B \rightarrow A \), and deduce from the first part that \( |B| \leq |A| \).
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