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Then/Now You added and subtracted polynomials. Add and subtract rational expressions with like denominators. Add and subtract rational expressions with unlike denominators.

Concept 1 Rule: If you have a common denominator, simply add or subtract numerators.

Example 1 Add Rational Expressions with Like Denominators The common denominator is 15. Add the numerators. Divide by the common factor, 5. Find Simplify.

Example 1 A. B. C. D. Find

Example 2 Subtract Rational Expressions with Like Denominators The common denominator is x – 3. The additive inverse of (x – 5) is –(x – 5). Distributive Property Find Simplify.

Example 2 Find A. B. 3(2y – 3) C. D.

Inverse Denominators Rewrite x – 11 as –(11 – x). Rewrite so the common denominators are the same. Subtract the numerators. Find Simplify.

Example 3 Find A. B. C. D.

Assignment –Page 716 –Problems 1 – 3 & 15 – 25 (odds)

Example 4A LCMs of Polynomials A. Find the LCM of 12b 4 c 5 and 32bc 2. 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: LCM = 2 ● 2 ● 2 ● 2 ● 2 ● 3 ● b ● b ● b ● b ● c ● c ● c ● c ● c or 96b 4 c 5 12b 4 c 5 = 2 ● 2 ● 3 ● b ● b ● b ● b ● c ● c ● c ● c ● c 32bc 2 = 2 ● 2 ● 2 ● 2 ● 2 ● b ● c ● c

Example 4B LCMs of Polynomials B. Find the LCM of x 2 – 3x – 28 and x 2 – 8x + 7. Express each polynomial in factored form. x 2 – 3x – 28 = (x – 7)(x + 4) x 2 – 8x + 7 = (x – 7)(x – 1) Answer: LCM = (x + 4)(x – 7)(x – 1) Use each factor the greatest number of times it appears.

Example 4A A. 35a 3 b 2 B. 7a 2 b 2 C. 14ab 2 D. 105a 3 b 4 A. Find the LCM of 21a 2 b 4 and 35a 3 b 2.

Example 4B A.(y + 6) 2 (y – 4) B.(y + 6) (y – 4) C.(y – 4) D.(y + 6) (y – 4) 2 B. Find the LCM of y y + 36 and y 2 + 2y – 24.

Concept 2

Example 5 Add Rational Expressions with Unlike Denominators Factor the denominators. The LCD is (x – 3) 2. (x + 3)(x – 3) = x 2 – 9 Find

Example 5 Add Rational Expressions with Unlike Denominators Add the numerators. Simplify. Answer:

Example 5 Find A. B. C. D.

Assignment –Page 716 –Problems 5 – 9 & 33 – 45 (skip 37 & 43)

Example 6A Add Rational Expressions A. BIKING For the first 15 miles, a biker travels at x miles per hour. Then, due to a downhill slope, the biker travels 2 miles at a speed that is 2 times as fast. Write an expression to represent how much time the biker is bicycling. UnderstandFor the first 15 miles the biker’s speed is x. For the last 2 miles, the biker’s speed is 2x.

Example 6A Add Rational Expressions PlanUse the formula to represent the time t of each section of the biker’s trip, with rate r and distance d. SolveTime to ride 15 miles: d = 15 mi, r = x Time to ride 2 miles: d = 2 mi, r = 2x

Example 6A Add Rational Expressions Total riding time: The LCD is 2x. Multiply. Simplify. Answer:

Example 6A Add Rational Expressions Simplify. Let x = 1 in the answer expression. CheckLet x = 1 in the original expression. Since the expressions have the same value for x = 1, they are equivalent. So, the answer is reasonable.

Example 6B Add Rational Expressions B. BIKING For the first 15 miles, a biker travels at x miles per hour. Then, due to a downhill slope, the biker travels 2 miles at a speed that is 2 times as fast. If the biker is bicycling at a rate of 8 miles per hour for the first 15 miles, find the total amount of time the biker is bicycling. Substitute 8 for x in the expression. Simplify Equation from part (a)

Example 6B Add Rational Expressions Answer: So, the biker is bicycling for 2 hours.

Example 6A A. EQUESTRIAN A rider is on a horse for 3 miles traveling at x miles per hour. Then for the last half mile of the ride, the horse doubles its speed when it sees the barn on the horizon. Write an expression to represent how much time the horse is galloping. A. B. C. D.

Example 6B A.0.22 hour B.0.56 hour C.1.02 hours D.0.15 hour B. EQUESTRIAN A rider is on a horse for 3 miles traveling at x miles per hour. Then for the last half mile of the ride, the horse doubles its speed when it sees the barn on the horizon. If the horse is galloping at a rate of 15 miles per hour for the first 3 miles, find the total amount of time the horse was galloping.

Example 7 Subtract Rational Expressions with Unlike Denominators Simplify. Write using the LCD, 8x.

Example 7 Subtract Rational Expressions with Unlike Denominators Answer: Subtract the numerators. Simplify.

Example 7 A. B. C. D.

Assignment –Page 716 –Problems 11, 13, 37, 43, 47, & 49