1. 5-Minute Check on Chapter 2 Transparency 3-1 Click the mouse button or press the Space Bar to display the answers. 1.Evaluate 42 - |x - 7| if x = -3 2.Find 4.1  (-0.5) Simplify each expression 3. 8(-2c + 5) + 9c 4. (36d – 18) / (-9) 5.A bag of lollipops has 10 red, 15 green, and 15 yellow lollipops. If one is chosen at random, what is the probability that it is not green? 6. Which of the following is a true statement Standardized Test Practice: ACBD 8/4 < 4/8-4/8 < -8/4-4/8 > -8/4-4/8 > 4/8

2. Lesson 12-7 Rational Expressions with Unlike Denominators

3. Transparency 7 Click the mouse button or press the Space Bar to display the answers.

4. Transparency 7a

5. Objectives Add rational expressions with unlike denominators Subtract rational expressions with unlike denominators

6. Vocabulary Least common multiple – Least common denominator –

7. Key Concept Step 1: Find the LCD –use least common multiples of denominator to find LCD Step 2: Change each rational expression into an equivalent expression with the LCD as the denominator –convert by multiplying top and bottom by another form of 1 Step 3: Add or subtract just as with rational expressions with like denominators –add or subtract numerators over the denominator Step 4: Simplify if necessary

8. Example 1 Find the LCM of Find the prime factors of each coefficient and variable expression. Use each prime factor the greatest number of times it appears in any of the factorizations. Answer:

9. Example 2 Find the LCM of Express each polynomial in factored form. Use each factor the greatest number of times it appears. Answer:

10. Example 3 Find Factor each denominator and find the LCD. Since the denominator of is already 5z, only needs to be renamed.

11. Example 3 cont Multiply by Distributive Property Add the numerators Answer: Simplify.

12. Example 4 Find Factor the denominators. The LCD is Add the numerators Simplify.Answer:

13. Example 5 Find Factor. The LCD is Add the numerators. Multiply. Simplify Answer:

14. Summary & Homework Summary: –Rewrite rational expressions with unlike denominators using the least common denominator (LCD). Then add or subtract Homework: –none