# Algebra: Evaluating Expressions

## Evaluating Expressions

I've used the word "evaluate" a lot so far, and as you've probably already figured out from context clues, it's just a fancy word for "give me the numeric answer."

**Example 7**: Evaluate the expression -2*x*^{2}*y* if *x* = 4 and *y* = -3.

**Solution**: Since you know the values of *x* and *y*, replace (substitute) the variables with the corresponding number. I usually use parentheses to surround numbers I substitute in, to make sure I don't screw up the signs.

- -2(4)
^{2}(-3)

Now, just apply the order of operations.

- -2(16)(-3) = (-32)(-3) = 96

##### You've Got Problems

Problem 7: Evaluate the expression *x*(*y* - 3)^{2} if *x* = 5 and *y* = -1.

Excerpted from The Complete Idiot's Guide to Algebra © 2004 by W. Michael Kelley. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with **Alpha Books**, a member of Penguin Group (USA) Inc.

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**See also:**