Basic Operations
Evaluating Functions
Functions are represented in math using parentheses such as f(x). This notation indicates “f†is a function of, or depends on, the variable x. A linear equation might be y = 2x – 4, while the equivalent function would be f(x) = 2x – 4. Both the equation and function would create the same table and the same graph. However, function notation states the input and the output at the same time, something the equation cannot do.
Example 1 Given f(x) = 3x – 4, find f(-2).
Step 1. Eliminate the input value “x†and replace it with parentheses.
f ( ) = 3( ) – 4
Step 2. Place the input value of -2 inside the parentheses.
f (-2) = 3(-2) – 4
Step 3. Simplify the right side of the equation.
f (-2) = -6 – 4
f (-2) = - 10
*Note: This is read, “The function f, with an input of -2, has an output of -10.
This can be graphed as the ordered pair (-2, -10).