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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 -2x2y 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.

CIG Algebra

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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