Exercise 1.6.6

(a)
Using the particular set A = { a , b , c } , exhibit two different 1 1 mappings from A into P ( A ) .
(b)
Letting C = { 1 , 2 , 3 , 4 } , produce an example of a 1 1 map g : C P ( C ) .
(c)
Explain why, in parts (a) and (b), it is impossible to construct mappings that are onto.

Answers

(a)
f ( x ) = { x } , f ( x ) = { x , b } for x b and f ( x ) = { a , b , c } for x = b .
(b)
f ( x ) = { x } .
(c)
We can hit at most n elements in the power set out of the 2 n total elements.
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2022-01-27 00:00
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