Common Algebra Mistakes
Example: Function Notation

The Goal

Compute f(g(4)) if f(4) = -4, g(4) = -2 and f(-2) = -1.

The Mistake

Find the algebra mistake:


(Roll the mouse over the algebra to see a hint in red)

The Correction


(Roll the mouse over the area above to see the correction in blue)

An Explanation

The expression f(g(4)) does not indicate the product of two function values. In other words, it is not equal to f(4) times g(4). Instead, f(g(4)) means to compute g(4) and plug the result into the function f(x). In this case g(4) = -2, so f(g(4)) = f(-2) = -1. This is an example of function composition.

Home Page | Common Algebra Mistakes | Privacy Policy

Valid HTML 4.01 Transitional