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Copyright © 2013, 2009, 2005 Pearson Education, Inc. Section 6.3 Addition and Subtraction of Rational Expressions.

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Presentation on theme: "Copyright © 2013, 2009, 2005 Pearson Education, Inc. Section 6.3 Addition and Subtraction of Rational Expressions."— Presentation transcript:

1 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Section 6.3 Addition and Subtraction of Rational Expressions

2 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Objectives Least Common Multiples Review of Addition and Subtraction of Fractions Addition of Rational Expressions Subtraction of Rational Expressions

3 Copyright © 2013, 2009, 2005 Pearson Education, Inc. The least common multiple (LCM) of two or more polynomials can be found as follows. Step 1: Factor each polynomial completely. Step 2: List each factor the greatest number of times that it occurs in either factorization. Step 3: Find the product of this list of factors. The result is the LCM. FINDING THE LEAST COMMON MULTIPLE

4 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Find the least common multiple of each pair of expressions. a. 6x, 9x 4 b. x 2 + 7x + 12, x 2 + 8x + 16 Solution Step 1: Factor each polynomial completely. 6x = 3 2 x9x 4 = 3 3 x x x x Step 2: List each factor the greatest number of times x x x x Step 3: The LCM is 18x 4.

5 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example (cont) b. x 2 + 7x + 12, x 2 + 8x + 16 Step 1: Factor each polynomial completely. x 2 + 7x + 12 = (x + 3)(x + 4) x 2 + 8x + 16 = (x+ 4)(x + 4) Step 2: List each factor the greatest number of times. (x + 3), (x + 4), and (x + 4) Step 3: The LCM is (x + 3)(x + 4) 2.

6 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Find the sum. a.b. Solution a. The LCD is 42. b. The LCD is 18.

7 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Find the difference. a.b. Solution a. The LCD is 36. b. The LCD is 60.

8 Copyright © 2013, 2009, 2005 Pearson Education, Inc. To add two rational expressions with like denominators, add their numerators. The denominator does not change. C not zero SUMS OF RATIONAL EXPRESSIONS

9 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Add and simplify. a.b. Solution a. b.

10 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Add and simplify. a.b. Solution a.b.

11 Copyright © 2013, 2009, 2005 Pearson Education, Inc. To subtract two rational expressions with like denominators, subtract their numerators. The denominator does not change. C not zero DIFFERENCES OF RATIONAL EXPRESSIONS

12 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Subtract and simplify. a.b. Solution a. b.

13 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Subtract and simplify. Solution The LCD is x(x + 7).

14 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example Simplify the expression. Write your answer in lowest terms and leave it in factored form. Solution

15 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Step 1: If the denominators are not common, multiply each expression by 1 written in the appropriate form to obtain the LCD. Step 2: Add or subtract the numerators. Combine like terms. Step 3: If possible, simplify the final expression. STEPS FOR FINDING SUMS AND DIFFERENCES OF RATIONAL EXPRESSIONS

16 Copyright © 2013, 2009, 2005 Pearson Education, Inc. Example A 75-watt light bulb with a resistance of R 1 = 160 ohms and a 60-watt light bulb with a resistance of R 2 = 240 ohms are placed in an electrical circuit. Find the combined resistance. Solution R = 96 ohms


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