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)


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