How Do You Evaluate a Function? I

This post about how you evaluate a function is part of a series of posts to help you prepare for the Advanced Algebra and Functions part of the Accuplacer test.

To evaluate a function means to find the function’s y-value if you are given an x-value.

Question

Let’s say you’re given this function:

and you’re asked to find f(10) — in other words, the value of f where x=10.

Solution

To do that, substitute 10 into the equation for f where you see x:

Now clean it up: Substitute 8 for 10-2:

And multiply 4 by 8:

So f(10)=32..

And that’s all there is to evaluating this function.

The example in this post is a linear function.

See How Do You Evaluate a Function? II for an example of how to evaluate a quadratic function.

This question is similar to question number 1 in the sample questions for the Accuplacer Advanced Algebra and Functions test.