We can define a function f : X Y by selecting the elements of X one by one and associating with each a unique element of Y.
For example, f(a) = q , f(b) = s and f(c) = p is a valid function definition,
and range (f) = { q, s, p } Y.
Note that the same function could be defined by a diagram:
For such a diagram to be valid function definition there must be one, and only one, arrow from every element x X.
Example 4.2 Let A = { a, b, c } , B = { d, e }
The diagram…
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