Chapter 7 Rational Expressions 7 1 Rational Functions

Chapter 7 Rational Expressions

§ 7. 1 Rational Functions and Simplifying Rational Expressions

Rational Expressions Rational expressions can be written in the form where P and Q are both polynomials and Q 0. Examples of Rational Expressions Martin-Gay, Beginning and Intermediate Algebra, 4 ed 3

Evaluating Rational Expressions To evaluate a rational expression for a particular value, substitute the replacement value into the rational expression and simplify the result. Example: Evaluate the following expression for y = 2. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 4

Evaluating Rational Expressions In the previous example, what would happen if we tried to evaluate the rational expression for y = 5? This expression is undefined! Martin-Gay, Beginning and Intermediate Algebra, 4 ed 5

Undefined Rational Expressions We have to be able to determine when a rational expression is undefined. A rational expression is undefined when the denominator is equal to zero. The numerator being equal to zero is okay (as the rational expression simply equals zero). Martin-Gay, Beginning and Intermediate Algebra, 4 ed 6

Undefined Rational Expressions Find any real numbers that make the following rational expression undefined. Example: The expression is undefined when 15 x + 45 = 0. So the expression is undefined when x = 3. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 7

Simplifying Rational Expressions Simplifying a rational expression means writing it in lowest terms or simplest form. To do this, we need to use the Fundamental Principle of Rational Expressions If P, Q, and R are polynomials, and Q and R are not 0, Martin-Gay, Beginning and Intermediate Algebra, 4 ed 8

Simplifying Rational Expressions Simplifying a Rational Expression 1) Completely factor the numerator and denominator. 2) Apply the Fundamental Principle of Rational Expressions to eliminate common factors in the numerator and denominator. Warning! Only common FACTORS can be eliminated from the numerator and denominator. Make sure any expression you eliminate is a factor. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 9

Simplifying Rational Expressions Example: Simplify the following expression. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 10

Simplifying Rational Expressions Example: Simplify the following expression. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 11

Simplifying Rational Expressions Example: Simplify the following expression. Martin-Gay, Beginning and Intermediate Algebra, 4 ed 12