Evaluating Functions

Recall from the linear unit that f(x) and y can be used interchangeably and that function notation is a shortened method of writing a function. Functions are represented using parentheses such as f(x). This notation indicates "f" is a function of, or depends on, the variable x. A quadratic equation might be y = x2 + 2x - 4, while the equivalent function would be f( x) = x2 + 2x - 4. Both the equation and the function create the same table and graph. However, function notation states the input and the output at the same time, something the equation cannot do.

The expression f(x) means "plug a value for x into the formula f "; the expression does not mean multiply f and x . In function notation, the x in f(x) is called the argument of the function, or just the argument. When given f(2), it means to replace any x in the function with 2 and then find the function's value.


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