If R is a binary relation on a set A define R–1 on A.
Let R = {(a, b) : a, b ϵ W and 3a + 2b = 15} and 3a + 2b = 15}, where W is the set of whole numbers.
Express R and R–1 as sets of ordered pairs.
Show that (i) dom (R) = range (R–1) (ii) range (R) = dom (R–1)
3a + 2b = 15
a=1 è b=6
a=3 è b=3
a=5 è b=0
R = {(1, 6), (3, 3), (5, 0)}
= {(6, 1), (3, 3), (0, 5)}
The domain of R is the set of first co-ordinates of R
Dom(R) = {1, 3, 5}
The range of R is the set of second co-ordinates of R
Range(R) = {6, 3, 0}
The domain of is the set of first co-ordinates of
Dom() = {6, 3, 0}
The range of is the set of second co-ordinates of
Range() = {1, 3, 5}
Thus,
dom (R) = range (R–1)
range (R) = dom (R–1)