Pre-Algebra Demystified

(Marvins-Underground-K-12) #1

To add or subtract like terms, add or subtract the numerical coefficients and
use the same variables.


EXAMPLE

Add 7yþ3y.


SOLUTION

7yþ3y¼ð 7 þ 3 Þy
¼10y

EXAMPLE

Subtract 8x5x.


SOLUTION

8x5x¼ð 8  5 Þx
¼3x

Adding or subtracting like terms is often called ‘‘combining like terms.’’

EXAMPLE

Combine like terms: 9xþ7x3x2x.


SOLUTION

9xþ7x3x2x¼ð 9 þ 7  3  2 Þx:
¼11x
Unlike terms cannot be added or subtracted. When an expression has both
like and unlike terms, it can be simplified by combining all like terms.


EXAMPLE

Combine like terms: 6x8xþ2y3yþ5x4y.


SOLUTION

6x8xþ2y3yþ5x4y¼6x8xþ5xþ2y3y4y
¼ð 6  8 þ 5 Þxþð 2  3  4 Þy
¼3xþð 5 Þy
¼3x5y

CHAPTER 7 Expression and Equations 131

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