Let A = {1, 2, 3, 4}. Let f : A A and g : A A,

defined by f = {(1, 4), (2, 1), (3,3),(4, 2)} and g = {(1, 3), (2, 1), (3, 2), (4, 4)}.


Find (i) g of (ii) f o g (iii) f o f.


(i) g o f


To find: g o f


Formula used: g o f = g(f(x))


Given: f = {(1, 4), (2, 1), (3, 3), (4, 2)} and g = {(1, 3), (2, 1),


(3, 2), (4, 4)}


Solution: We have,


gof(1) = g(f(1)) = g(4) = 4


gof(2) = g(f(2)) = g(1) = 3


gof(3) = g(f(3)) = g(3) = 2


gof(4) = g(f(4)) = g(2) = 1


Ans) g o f = {(1, 4), (2, 3), (3, 2), (4, 1)}


(ii) f o g


To find: f o g


Formula used: f o g = f(g(x))


Given: f = {(1, 4), (2, 1), (3, 3), (4, 2)} and g = {(1, 3), (2, 1),


(3, 2), (4, 4)}


Solution: We have,


fog(1) = f(g(1)) = f(3) = 3


fog(2) = f(g(2)) = f(1) = 4


fog(3) = f(g(3)) = f(2) = 1


fog(4) = f(g(4)) = f(4) = 2


Ans) f o g = {(1, 3), (2, 4), (3, 1), (4, 2)}


(iii) f o f


To find: f o f


Formula used: f o f = f(f(x))


Given: f = {(1, 4), (2, 1), (3, 3), (4, 2)}


Solution: We have,


fof(1) = f(f(1)) = f(4) = 2


fof(2) = f(f(2)) = f(1) = 4


fof(3) = f(f(3)) = f(3) = 3


fof(4) = f(f(4)) = f(2) = 1


Ans) f o f = {(1, 2), (2, 4), (3, 3), (4, 1)}


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