Adding and Subtracting Rational Expressions Lesson 3.10 Page 171

Example 1: (Adding-Like)

Example 2: (Adding-Like)

Example 3: (Subtracting-Like)

Example 4: (Subtracting-Like)

What happens if the denominators are not the same? You must make them the same by finding a least common denominator (LCD)!

Definition: LCD Least Common Denominator The least common denominator (LCD) of two or more rational expressions is the product of the factors of the rational expressions with each common factor used only once. 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, , 28, 42, 56, 70, 84, 98, 112, 126, 140

Example 5: (Adding-Unlike)

Adding or Subtracting Rational Expressions with Different Denominators Find the least common denominator (LCD). Rewrite each rational expression as an equivalent fraction with the least common denominator as the denominator. Add or subtract the numerators to get the numerator sum or difference. The least common denominator is the denominator. Write the answer in lowest terms.

Example 6: (Adding-Unlike)

Example 7: (Subtracting-Unlike) First factor the denominators.

Rewrite each rational expression as an equivalent fraction with the least common denominator as the denominator.

Subtract the numerators. The least common denominator is the denominator.

Finally write the answer in lowest terms.

Homework Assignment: Page 173# 1 – 6 all # 13 – 18 all