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Question of 100

Q.Consider the set A={−1,1}A = \{-1, 1\}

a) Write all elements in A×AA \times A.
(1)
b) How many relations are there from AA to AA?
(1)
c) Write all functions from AA to AA which has Range ={−1,1}= \{-1, 1\}. (2)
Kerala DhseKerala DHSE Plus One Board 2019Subjective· 4mImportance★★★★★
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List the ordered pairs of A×AA\times A; the number of relations is 22 raised to the size of A×AA\times A; the functions with full range must send −1-1 and 11 to different values.

Given A={−1,1}A=\{-1,1\}.

a) A×AA\times A

A×A={(−1,−1), (−1,1), (1,−1), (1,1)}A\times A = \{(-1,-1),\,(-1,1),\,(1,-1),\,(1,1)\}

b) Number of relations from AA to AA

A relation from AA to AA is any subset of A×AA\times A. Since n(A×A)=4n(A\times A)=4, the number of subsets (relations) is

24=162^4 = 16

c) Functions from AA to AA with Range ={−1,1}=\{-1,1\}

A function assigns exactly one image to each of −1-1 and 11. All possible functions:

  • −1↦−1, 1↦−1-1\mapsto-1,\ 1\mapsto-1 — range {−1}\{-1\}, not full …

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