Trigonometry Workbook For Dummies
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Whether you add or subtract variables, you follow the same rule, even though they have different operations: when adding or subtracting terms that have exactly the same variables, you either add or subtract the coefficients, and let the result stand with the variable.

For example:

  • Addition. In this equation, you can add all of the coefficients (2, 5, and 4) because the variables are the same (a).

    2a + 5a + 4a = 11a

  • Subtraction. In this equation, you can subtract all of the coefficients (11, 5, and 4) because the variables are the same (a).

    11a – 5a – 4a = 2a

If no number appears before the variable, then you can assume that the number is 1. So a = 1a and x = 1x.

You add terms that have the same variables because they represent the same amounts. You don’t try to add the terms with different variables. The examples that follow involve two or more variables:

  • Two variables.

    a + 3a + x + 2x

    (1a + 3a) + (1x + 2x)

    4a + 3x

  • Three variables.

    5a + 2a + 6b + 8b + 11c

    (5a + 2a) + (6b + 8b) + 11c

    7a + 14b + 11c

About This Article

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About the book author:

Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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