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)}