Discrete Mathematics with Applications 4th Edition

Published by Cengage Learning
ISBN 10: 0-49539-132-8
ISBN 13: 978-0-49539-132-6

Chapter 7 - Functions - Exercise Set 7.1 - Page 396: 43

Answer

$F(A) \cap F(B) \nsubseteq F(A \cap B) $ $counter\,example$ $X=\left \{ 5,6 \right \},Y=\left \{ 5 \right \}\\ A=\left \{ 5 \right \},B=\left \{ 6 \right \}\\ F:X\rightarrow Y ,\,\,\,F(5)=F(6)=5 \\ F(A) \cap F(B)=F(\left \{ 5 \right \})\cap F(\left \{ 6 \right \})=\left \{ 5 \right \}\\ A \cap B=\left \{ 5 \right \}\cap \left \{ 6 \right \}=\varnothing \\ F(A \cap B)=F(\varnothing )=\varnothing \\ but\,\left \{ 5 \right \}\nsubseteq \varnothing \\ F(A) \cap F(B) \nsubseteq F(A \cap B) $

Work Step by Step

$X=\left \{ 5,6 \right \},Y=\left \{ 5 \right \}\\ A=\left \{ 5 \right \},B=\left \{ 6 \right \}\\ F:X\rightarrow Y ,\,\,\,F(5)=F(6)=5 \\ F(A) \cap F(B)=F(\left \{ 5 \right \})\cap F(\left \{ 6 \right \})=\left \{ 5 \right \}\\ A \cap B=\left \{ 5 \right \}\cap \left \{ 6 \right \}=\varnothing \\ F(A \cap B)=F(\varnothing )=\varnothing \\ but\,\left \{ 5 \right \}\nsubseteq \varnothing \\ F(A) \cap F(B) \nsubseteq F(A \cap B) $
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