Rational Expressions with Like Denominators ALGEBRA 1B

Objective Add and subtract rational expressions with like denominators.

Introduction To add or subtract fractions with like denominators, you add or subtract the numerators. Then you write the sum or difference over the common denominator. You can use these same methods to add or subtract rational expressions.

Ex. 1: Find Since x + 2 is the common denominator, add the numerators.

Ex. 2: Find Add the additive inverse of a - 3. Distributive Property Remember when subtracting rational expressions to add the additive inverse of the second expression.

Express in simplest form. When adding or subtracting fraction, sometimes the result can be expressed in simplest form. The GCF of 4 and 8 is 4. The GCF of 6 and 16 is 2.

Ex. 3: Find Since 3n+4 is the common denominator, subtract the numerators. Combine like terms. Factor out a 2 out of the numerator and cancel 3n+4 from both numerator and denominator.

Ex. 4: Find Rewrite 2 – x as x – 2 by multiplying by -1. Remember Simplify and combine like terms.

Example 5: Application Find the measure of the perimeter of the rectangle.

Ex. 5: Find the measure of the perimeter of the rectangle. ← Perimeter formula for rectangle. ← Substitute values. ← Distributive Property ← Combine like terms ← Factor out 2 as common factor and cancel terms that are same in numerator and denominator. The measure of the perimeter is: