# 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.

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