Functions

A function is a relationship between two sets of numbers. We may think of this as a mapping; a function maps a number in one set to a number in another set. Notice that a function maps values to one and only one value. Two values in one set could map to one value, but one value must never map to two values: that would be a relation, not a function.

For example, if we write (define) a function as:

f(x) = x2

then we say:

'f of x equals x squared'

and we have

f( - 1) = 1

f(1) = 1

f(7) = 49

f(1 / 2) = 1 / 4

f(4) = 16

and so on.