Question:
Let $A=\{1,2,3,4,6\}$ and $R=\{(a, b): a, b \in A$, and a divides b $\} .$
(i) Write $\mathbf{R}$ in roster form.
(ii) Find dom (R) and range (R).
Solution:
Given: A = {1, 2, 3, 4, 6}
(i) $R=\{(a, b): a, b \in A$, and a divides $b\}$
R is Foster Form is,
$R=\{(1,2),(1,3),(1,4),(1,6),(2,2),(2,4),(2,6),(3,3),(3,6),(4,4),(6,6)\}$
(ii) Dom(R) $=\{1,2,3,4,6\}$
Range(R) = {2, 3, 4, 6}