Question:
Determine the domain and range of the following relations:
(i) $R=\{(a, b): a \in N, a<5, b=4\}$
(ii) $S=\{(a, b): b=|a-1|, a \in Z$ and $|a| \leq 3\}$
Solution:
(i) R = {(a, b) : a ∈ N, a < 5, b = 4}
We have:
a = 1, 2, 3, 4
b = 4
R = {(1, 4), (2, 4), (3, 4), (4, 4)}
Domain (R) = {1, 2, 3, 4}
Range (R) = {4}
(ii) $S=\{(a, b): b=|a-1|, a \in Z$ and $|a| \leq 3\}$
Now,
$a=-3,-2,-1,0,1,2,3$
$b=|-3-1|=4$
$b=|-2-1|=3$
$b=|-1-1|=2$
$b=|0-1|=1$
$b=|1-1|=0$
$b=|2-1|=1$
$b=|3-1|=2$
Thus, we have:
b = 4, 3, 2, 1, 0, 1, 2
Or,
$S=\{(-3,4),(-2,3),(-1,2),(0,1),(1,0),(2,1),(3,2)\}$
Domain $(S)=\{-3,-2,-1,0,1,2,3\}$
Range $(S)=\{0,1,2,3,4\}$