9.3 Simplifying and Multiplying Rational Expressions 4/13/2014
Rational Expression: an expression that is the ratio of two polynomials. It is "Rational" because one is divided by the other, like a ratio. the polynomial you are dividing by cannot be zero. Note: Ex:
Simplify the rational expression, if possible. Example 1 Simplify a Rational Expression Simplify the rational expression, if possible. 15x = • 3 5 x 5 Divide out the common factor 5 and simplify. a. =3𝑥 5 b. x x 5 + This expression is already in simplest form. c. 14x2 6x 2 7 x x = • 2 3 x Divide out the common factors 2 and x. = 3 7𝑥 3
Simplify the expression, if possible. Checkpoint Simplify a Rational Expression Simplify the expression, if possible. 4x ANSWER 2x 5 1. 10 2. 8 4x ANSWER 2 x 9x ( 12 1 x + 3. ANSWER 3x ( 4 1 x + x 1 – 4. ANSWER already in simplest form
Simplify the expression, if possible. Checkpoint Write in Simplest Form Simplify the expression, if possible. 2x 1 + 5. ANSWER already in simplest form 6. 3x ( ) 1 x + 3x 2 ANSWER x ( ) 1 +
Simplify the expression, if possible. Checkpoint Write in Simplest Form Simplify the expression, if possible. 2x 2 + 8x 7. 12x ANSWER 6 4 x + 8. 2 x + 6 3x ANSWER 3 1
Multiply . Simplify the result. • 3x 8x 5 Example 3 Multiply Rational Expressions 4x 2 9x Multiply . Simplify the result. • 3x 8x 5 SOLUTION 3x 4x 2 9x • 8x 5 1 3 1 2 = 3 𝑥 2 2 𝑥 5 Subtract exponents of x = 2x 3 3 7
Multiply . Simplify the result. • x x 2 9 – 4x 3x 12 Example 4 Multiply Rational Expressions Multiply . Simplify the result. • x x 2 9 – 4x 3x 12 SOLUTION • x x 2 9 – 4x 3x 12 Factor the numerators and denominators. = 4 3x ( ) 3 x – + • = 4 ( ) 3 x + 8
Multiply the rational expressions. Simplify the result. Checkpoint Multiply Rational Expressions Multiply the rational expressions. Simplify the result. 9. 14 3x 7x • 6x 3 ANSWER 4x 1 • x 2 2x 4 – 3x 6 10. ANSWER 3x 4 • x 2 6x 4 – 11. 4x 8 + x 3 ANSWER 24 x 2 ( ) 2 x –
Multiply . Simplify the result. • 3 ( 2 – x ( Example 5 Multiply by a Polynomial x x 2 – 6 5x + Multiply . Simplify the result. • 3 ( 2 – x ( SOLUTION • x x 2 + 5x 6 ( 2 – 3 Write polynomial as a rational expression. = • 1 x x 2 + 5x 6 ( 2 – 3 Factor out of . 1 – ( 2 x = • x 2 3 Simplify. = x – 3x 3 10
Multiply the expressions. Simplify the result. Checkpoint Multiply by a Polynomial Multiply the expressions. Simplify the result. x + 4 12. 2x ( • 3 6 ANSWER 8 x 13. 3x + x 2 ( • 12 4x ANSWER x 2 3 3x 14. x 2 • – ( 2 x ANSWER x 3x – + 1
Homework: 9.3 p.483 #22-52 even only I’m reading a book about anti-gravity. I can’t put it down!!!