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Composition of Functions of Set
Two functions f: A → B and g: B → C can be composed to give a composition g o f. This is a function from A to C defined by (g o f)(x) = g(f(x))
Example
Let f(x) = x + 2 and g(x) = 2x + 1, find (f o g)(x) and (g o f)(x).
Solution
(f o g)(x) = f(g(x)) = f(2x + 1) = 2x + 1 + 2 = 2x + 3
(g o f)(x) = g (f(x)) = g(x + 2) = 2 (x+2) + 1 = 2x + 5
Hence, (f o g)(x) ≠ (g o f)(x)
Some Facts about Composition
If f and g are one-to-one then the function (g o f) is also one-to-one.
If f and g are onto then the function (g o f) is also onto.
Composition always holds associative property but does not hold commutative property.
Updated on: 23-Aug-2019
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