1 transitive but neither symmetric nor reflexive
2 reflexive but neither symmetric nor transitive
3 an equivalence relation
4 symmetric but neither reflexive nor transitive
Explanation:
D \(\mathrm{A}=\{1,2,3,4,5,6,7\}\). defined on the set
\(\mathrm{R}=\{(\mathrm{x}, \mathrm{y}) \in \mathrm{A} \times \mathrm{A}: \mathrm{x}+\mathrm{y}=7\}\)
\(\mathrm{R}=\{(1,6),(2,5),(3,4),(4,3),(5,2),(6,1)\}\)
For symmetric:- \(\mathrm{xRy}=\mathrm{yRx}\)
\((1,6) \in R,(6,1) \in R\) and \((5,2) \in R,(2,5) \in R\)
So \(\mathrm{R}\) is symmetric
For Reflexive:- \(\mathrm{xRx}\)
\((1,1) \notin \mathrm{R}(2,2) \notin \mathrm{R}(3,3) \notin \mathrm{R}\) and \((5,5) \notin \mathrm{R}\)
So, \(\mathrm{R}\) is not reflexive
For transitive
\((1,6) \in R\) and \((6,1) \in R\) but \((1,1) \notin R\) and \((2,5) \in R\)
\((5,2) \in R\) but \((2,2) \notin R\) so \(R\) is not transitive.