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Question
A = {1, 2, 3, 5} and B = {4, 6, 9}. Define a relation R from A to B by R = {(x, y): the difference between x and y is odd; x ∈ A, y ∈ B}. Write R in roster form.
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Solution 1
Given: A = {1, 2, 3, 5} and B = {4, 6, 9}
R = {(x, y): the difference between x and y is odd; x ∈ A, y ∈ B}
= {(x, y) : y - x = odd; x ∈ A, y ∈ B}
∴ R = {(1, 4), (1, 6), (2, 9), (3, 4), (3, 6), (5, 4), (5, 6)}
Solution 2
A = [1, 2, 3, 5] and B = [4, 6, 9]
R = {(x, y) : the difference between x and y is odd, x ∈ A, y ∈ B}
For x = 1,
4 - 1 = 3 and 6-1 = 5
y = 4, 6
For x = 2,
9 -2 = 7
y = 9
For x = 3,
4 -3 = 1 and 6 -3 = 3
y = 4, 6
For x = 5,
5 - 4=1 and 6 -5 =1
y = 4, 6
Thus, we have:
R = {(1, 4), (1, 6), (2, 9), (3, 4), (3, 6), (5, 4), (5, 6)}
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