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Q30E
Expert-verifiedLet \({R_1} = \{ (1,2),(2,3),(3,4)\} \) and \({R_2} = \{ (1,1),(1,2),(2,1),(2,2),(2,3),\)\((3,1),(3,2),(3,3),(3,4)\} \) be relations from \(\{ 1,2,3\} \) to \(\{ 1,2,3,4\} \). Find
a) \({R_1} \cup {R_2}\).
b) \({R_1} \cap {R_2}\).
c) \({R_1} - {R_2}\).
d) \({R_2} - {R_1}\).
(a) \({R_1} \cup {R_2} = \{ (1,1),(1,2),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3),(3,4)\} \)
(b) \({R_1} \cap {R_2} = \{ (1,2),(2,3),(3,4)\} \)
(c) \({R_1} - {R_2} = \emptyset \)
(d) \({R_2} - {R_1} = \{ (1,1),(2,1),(2,2),(3,1),(3,2),(3,3)\} \)
\(\begin{array}{l}{R_1} = \{ (1,2),(2,3),(3,4)\} \\{R_2} = \{ (1,1),(1,2),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3),(3,4)\} \end{array}\)
Union \(A \cup B\): All elements that are either in \(A\)or in \(B\)
Intersection \(A \cap B\): All elements that are both in \(A\)and in \(B\).
Difference \(A - B\): All elements in \(A\) that are NOT in \(B\)
(a)
The union of two relations contains all ordered pairs that are in either relation.
\({R_1} \cup {R_2} = \{ (1,1),(1,2),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3),(3,4)\} \)
(b)
The intersection of two relations contains all ordered pairs that are in both relations. We note that all ordered pairs in \({R_1}\)also occur in \({R_2}\).
\({R_1} \cap {R_2} = \{ (1,2),(2,3),(3,4)\} \)
(c)
\({R_1} - {R_2}\)contains all ordered pairs that are in the relation \({R_1}\) that do not occur in the relation \({R_2}\). We note that all ordered pairs in \({R_1}\) also occur in \({R_2}\), thus the difference \({R_1} - {R_2}\) does not contain any elements.
\({R_1} - {R_2} = \emptyset \)
(d)
\({R_2} - {R_1}\) contains all ordered pairs that are in the relation \({R_1}\)that do not occur in the relation \({R_2}\).
\({R_2} - {R_1} = \{ (1,1),(2,1),(2,2),(3,1),(3,2),(3,3)\} \)
Therefore,
(a) \({R_1} \cup {R_2} = \{ (1,1),(1,2),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3),(3,4)\} \)
(b) \({R_1} \cap {R_2} = \{ (1,2),(2,3),(3,4)\} \)
(c) \({R_1} - {R_2} = \emptyset \)
(d) \({R_2} - {R_1} = \{ (1,1),(2,1),(2,2),(3,1),(3,2),(3,3)\} \)
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