# + Adding and Subtracting. + How do you add or subtract fractions?

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+ How do you add or subtract fractions?

+ Adding and Subtracting Rational Expressions:  The addition and subtraction of fractions can be carried out only when their denominators are identical.  To get a required denominator, we may build up the denominator of a fraction.  We multiply the numerator and denominator of a fraction by the same number (not zero) to get an equivalent fraction. Definition: Addition and Subtraction of Rational Numbers If a/b and c/b are rational numbers, then and

+ Example:

+ Adding and Subtracting with Unlike Denominators  For fractions with different denominators, we build up one or both denominators to make the denominators the equal.  The least common denominator (LCD) is the smallest number that is a multiple of all of the denominators. Procedure: Finding the LCD 1.Factor each denominator completely. 2.Write a product using each factor that appears in a denominator. 3.For each factor, use the highest power of that factor that occurs in the denominators.

+ Example: Combine the fractions: Solution:

+ Example: Combine the fractions: Solution:

+ Example: Combine the fractions: Solution:

+ Example: Combine the fractions: Solution:

+ Assignment