A function is a relation (usually an equation) in which no two ordered pairs have the same x-coordinate when graphed.
One way to tell if a graph is a function is the vertical line test, which says if it is possible for a vertical line to meet a graph more than once, the graph is not a function.
Functions are usually denoted by letters such as f or g. If the first coordinate of an ordered pair is represented by x, the second coordinate (the y coordinate) can be represented by f(x).
When a function is an equation, the domain is the set of numbers that are replacements for x that give a value for f(x) that is on the graph.
Example 1:
For f(x) = 2x+6, find f(5)
f(x) = 2x+6 = 2x5+6 = 10 + 6 = 16
Example 2:
Find the domain of the function f(x) = 4/x
x can take any value except zero. Since division by 0 is not defined.
Therefore, the domain is said to be x > 0 and x < 0.
Directions: Answer the following questions. Also write at least 10 examples of your own.