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Holt McDougal Algebra 1 7-8 Multiplying Polynomials 7-8 Multiplying Polynomials Holt Algebra 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Lesson Quiz Lesson Quiz Holt McDougal Algebra 1

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7-8 Multiplying Polynomials Warm Up Evaluate. 1. 3 2 3. 10 2 Simplify. 4. 2 3 2 4 6. (5 3 ) 2 9 16 100 2727 2. 242. 24 5. y 5 y 4 5656 7. ( x 2 ) 4 8. –4( x – 7) –4 x + 28 y9y9 x8x8

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply polynomials. Objective

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials To multiply monomials and polynomials, you will use some of the properties of exponents that you learned earlier in this chapter.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 1: Multiplying Monomials A. (6y 3 )(3y 5 ) (6 y 3 )(3 y 5 ) 18 y 8 Group factors with like bases together. B. (3mn 2 ) (9m 2 n) (3 mn 2 )(9 m 2 n ) 27 m 3 n 3 Multiply. Group factors with like bases together. Multiply. (6 3)( y 3 y 5 ) (3 9)( m m 2 )( n 2 n )

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials When multiplying powers with the same base, keep the base and add the exponents. x 2 x 3 = x 2+3 = x 5 Remember!

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 1 Multiply. a. (3x 3 )(6x 2 ) (3 x 3 )(6 x 2 ) (3 6)( x 3 x 2 ) 18 x 5 Group factors with like bases together. Multiply. Group factors with like bases together. Multiply. b. (2r 2 t)(5t 3 ) (2 r 2 t )(5 t 3 ) (2 5)( r 2 )( t 3 t ) 10 r 2 t 4

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 1 Continued Multiply. Group factors with like bases together. Multiply. c. 4522 1 12 3 xzyzx y 3 2 1 3 x y x z y z 2453 32245 1 12 z 3 zx y 755 4 xyz

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials To multiply a polynomial by a monomial, use the Distributive Property.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 2A: Multiplying a Polynomial by a Monomial 4(3x 2 + 4x – 8) (4)3 x 2 +(4)4 x – (4)8 12 x 2 + 16 x – 32 Multiply. Distribute 4.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials 6pq(2p – q) (6 pq )(2 p – q ) Multiply. Example 2B: Multiplying a Polynomial by a Monomial (6 pq )2 p + (6 pq )(– q ) (6 2)( p p )( q ) + (–1)(6)( p )( q q ) 12 p 2 q – 6 pq 2 Group like bases together. Multiply. Distribute 6pq.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 2C: Multiplying a Polynomial by a Monomial Group like bases together. Multiply. 2 1 6 2 x y 8 22 2 2 6 1 2 yx 8 2 2 2 1 6 2 8 2 2 1 2 x 2 x 1 6 2 y x 2 y y 2 8 1 2 3x 3 y 2 + 4x 4 y 3 Distribute. 2 1 x y 2

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 2 Multiply. a. 2(4x 2 + x + 3) 2(4 x 2 + x + 3) 2(4 x 2 ) + 2( x ) + 2(3) 8 x 2 + 2 x + 6 Multiply. Distribute 2.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 2 Multiply. b. 3ab(5a 2 + b) 3 ab (5 a 2 + b ) (3 ab )(5 a 2 ) + ( 3ab )( b ) (3 5)( a a 2 )( b ) + (3)( a )( b b ) 15 a 3 b + 3 ab 2 Group like bases together. Multiply. Distribute 3ab.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 2 Multiply. c. 5r 2 s 2 (r – 3s) 5 r 2 s 2 ( r – 3 s ) (5 r 2 s 2 )( r ) – (5 r 2 s 2 )(3 s ) (5)( r 2 r )( s 2 ) – (5 3)( r 2 )( s 2 s ) 5 r 3 s 2 – 15 r 2 s 3 Group like bases together. Multiply. Distribute 5r 2 s 2.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials To multiply a binomial by a binomial, you can apply the Distributive Property more than once: (x + 3)(x + 2) = x(x + 2) + 3(x + 2) Multiply. Combine like terms. = x(x + 2) + 3(x + 2) = x(x) + x(2) + 3(x) + 3(2) = x 2 + 2x + 3x + 6 = x 2 + 5x + 6 Distribute. Distribute again.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Another method for multiplying binomials is called the FOIL method. 4. Multiply the Last terms. (x + 3)(x + 2) 3 2 = 6 3. Multiply the Inside terms. (x + 3)(x + 2) 3 x = 3x 2. Multiply the Outside terms. (x + 3)(x + 2) x 2 = 2x F O I L (x + 3)(x + 2) = x 2 + 2x + 3x + 6 = x 2 + 5x + 6 F OIL 1. Multiply the First terms. (x + 3)(x + 2) x x = x 2

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 3A: Multiplying Binomials (s + 4)(s – 2) s ( s – 2) + 4( s – 2) s ( s ) + s (–2) + 4( s ) + 4(–2) s 2 – 2 s + 4 s – 8 s 2 + 2 s – 8 Distribute. Distribute again. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 3B: Multiplying Binomials (x – 4) 2 ( x – 4)( x – 4) ( x x ) + ( x (–4)) + (–4 x ) + (–4 (–4)) x 2 – 4 x – 4 x + 16 x 2 – 8 x + 16 Write as a product of two binomials. Use the FOIL method. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Example 3C: Multiplying Binomials Multiply. (8m 2 – n)(m 2 – 3n) 8 m 2 ( m 2 ) + 8 m 2 (–3 n ) – n ( m 2 ) – n (–3 n ) 8 m 4 – 24 m 2 n – m 2 n + 3 n 2 8 m 4 – 25 m 2 n + 3 n 2 Use the FOIL method. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials In the expression ( x + 5) 2, the base is ( x + 5). ( x + 5) 2 = ( x + 5)( x + 5) Helpful Hint

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 3a Multiply. (a + 3)(a – 4) a ( a – 4)+3( a – 4) a ( a ) + a (–4) + 3( a ) + 3(–4) a 2 – a – 12 a 2 – 4 a + 3 a – 12 Distribute. Distribute again. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 3b Multiply. (x – 3) 2 ( x – 3)( x – 3) ( x x ) + ( x (–3)) + (–3 x ) + (–3)(–3) ● x 2 – 3 x – 3 x + 9 x 2 – 6 x + 9 Write as a product of two binomials. Use the FOIL method. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 3c Multiply. (2a – b 2 )(a + 4b 2 ) 2 a ( a ) + 2 a (4 b 2 ) – b 2 ( a ) + (– b 2 )(4 b 2 ) 2 a 2 + 8 ab 2 – ab 2 – 4 b 4 2 a 2 + 7 ab 2 – 4 b 4 Use the FOIL method. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials To multiply polynomials with more than two terms, you can use the Distributive Property several times. Multiply (5 x + 3) by (2 x 2 + 10 x – 6): (5x + 3)(2x 2 + 10x – 6) = 5x(2x 2 + 10x – 6) + 3(2x 2 + 10x – 6) = 5x(2x 2 + 10x – 6) + 3(2x 2 + 10x – 6) = 5x(2x 2 ) + 5x(10x) + 5x( – 6) + 3(2x 2 ) + 3(10x) + 3( – 6) = 10x 3 + 50x 2 – 30x + 6x 2 + 30x – 18 = 10x 3 + 56x 2 – 18

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials You can also use a rectangle model to multiply polynomials with more than two terms. This is similar to finding the area of a rectangle with length (2 x 2 + 10 x – 6) and width (5 x + 3): 2x22x2 +10x –6–6 10x 3 50x 2 – 30x 30x6x26x2 – 18 5x5x +3 Write the product of the monomials in each row and column: To find the product, add all of the terms inside the rectangle by combining like terms and simplifying if necessary. 10x 3 + 6x 2 + 50x 2 + 30x – 30x – 18 10x 3 + 56x 2 – 18

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Another method that can be used to multiply polynomials with more than two terms is the vertical method. This is similar to methods used to multiply whole numbers. 2x 2 + 10x – 6 5x + 3 6x 2 + 30x – 18 + 10x 3 + 50x 2 – 30x 10x 3 + 56x 2 + 0x – 18 10x 3 + 56x 2 + – 18 Multiply each term in the top polynomial by 3. Multiply each term in the top polynomial by 5x, and align like terms. Combine like terms by adding vertically. Simplify.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 4A: Multiplying Polynomials (x – 5)(x 2 + 4x – 6) x ( x 2 + 4 x – 6) – 5( x 2 + 4 x – 6) x ( x 2 ) + x (4 x ) + x (–6) – 5( x 2 ) – 5(4 x ) – 5(–6) x 3 + 4 x 2 – 5 x 2 – 6 x – 20 x + 30 x 3 – x 2 – 26 x + 30 Distribute x. Distribute x again. Simplify. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 4B: Multiplying Polynomials (2x – 5)(–4x 2 – 10x + 3) –4 x 2 – 10 x + 3 2 x – 5 x 20 x 2 + 50 x – 15 + –8 x 3 – 20 x 2 + 6 x –8 x 3 + 56 x – 15 Multiply each term in the top polynomial by –5. Multiply each term in the top polynomial by 2x, and align like terms. Combine like terms by adding vertically.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Multiply. Example 4C: Multiplying Polynomials (x + 3) 3 [ x · x + x (3) + 3( x) + (3)(3)] [ x ( x +3) + 3( x+ 3)]( x + 3) ( x 2 + 3 x + 3 x + 9)( x + 3) ( x 2 + 6 x + 9)( x + 3) Write as the product of three binomials. Use the FOIL method on the first two factors. Multiply. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Example 4C: Multiplying Polynomials Continued Multiply. (x + 3) 3 x 3 + 6 x 2 + 9 x + 3 x 2 + 18 x + 27 x 3 + 9 x 2 + 27 x + 27 x ( x 2 ) + x (6x) + x (9) + 3( x 2 ) + 3(6 x ) + 3(9) x ( x 2 + 6 x + 9) + 3( x 2 + 6 x + 9) Use the Commutative Property of Multiplication. Distribute. Distribute again. ( x + 3)( x 2 + 6 x + 9) Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Example 4D: Multiplying Polynomials Multiply. (3x + 1)(x 3 + 4x 2 – 7) x3x3 –4x 2 –7–7 3x43x4 –12x 3 –21x –4x 2 x3x3 –7–7 3x3x +1 3 x 4 – 12 x 3 + x 3 – 4 x 2 – 21 x – 7 Write the product of the monomials in each row and column. Add all terms inside the rectangle. 3 x 4 – 11 x 3 – 4 x 2 – 21 x – 7 Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials A polynomial with m terms multiplied by a polynomial with n terms has a product that, before simplifying has mn terms. In Example 4A, there are 2 3, or 6 terms before simplifying. Helpful Hint

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 4a Multiply. (x + 3)(x 2 – 4x + 6) x ( x 2 – 4 x + 6) + 3( x 2 – 4 x + 6) Distribute. Distribute again. x ( x 2 ) + x (–4 x ) + x (6) +3( x 2 ) +3(–4 x ) +3(6) x 3 – 4 x 2 + 3 x 2 +6 x – 12 x + 18 x 3 – x 2 – 6 x + 18 Simplify. Combine like terms.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 4b Multiply. (3x + 2)(x 2 – 2x + 5) x 2 – 2 x + 5 3 x + 2 Multiply each term in the top polynomial by 2. Multiply each term in the top polynomial by 3x, and align like terms. 2 x 2 – 4 x + 10 + 3 x 3 – 6 x 2 + 15 x 3 x 3 – 4 x 2 + 11 x + 10 Combine like terms by adding vertically.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Example 5: Application The width of a rectangular prism is 3 feet less than the height, and the length of the prism is 4 feet more than the height. a. Write a polynomial that represents the area of the base of the prism. Write the formula for the area of a rectangle. Substitute h – 3 for w and h + 4 for l. A = l w A = l w A = ( h + 4)( h – 3) Multiply. A = h 2 + 4 h – 3 h – 12 Combine like terms. A = h 2 + h – 12 The area is represented by h 2 + h – 12.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Example 5: Application Continued The width of a rectangular prism is 3 feet less than the height, and the length of the prism is 4 feet more than the height. b. Find the area of the base when the height is 5 ft. A = h 2 + h – 12 A = 5 2 + 5 – 12 A = 25 + 5 – 12 A = 18 Write the formula for the area the base of the prism. Substitute 5 for h. Simplify. Combine terms. The area is 18 square feet.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 5 The length of a rectangle is 4 meters shorter than its width. a. Write a polynomial that represents the area of the rectangle. Write the formula for the area of a rectangle. Substitute x – 4 for l and x for w. A = l w A = x ( x – 4) Multiply. A = x 2 – 4 x The area is represented by x 2 – 4 x.

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials Check It Out! Example 5 Continued The length of a rectangle is 4 meters shorter than its width. b. Find the area of a rectangle when the width is 6 meters. A = x 2 – 4x A = 36 – 24 A = 12 Write the formula for the area of a rectangle whose length is 4 meters shorter than width. Substitute 6 for x. Simplify. Combine terms. The area is 12 square meters. A = 6 2 – 4 6

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials 7.8 Homework: Part I Multiply. 1. (6 s 2 t 2 )(3 st ) 2. 4 xy 2 ( x + y ) 3. ( x + 2)( x – 8) 4. (2 x – 7)( x 2 + 3 x – 4) 5. 6 mn ( m 2 + 10 mn – 2) 6. (2 x – 5 y )(3 x + y )

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Holt McDougal Algebra 1 7-8 Multiplying Polynomials 7.8 Homework: Part II 7. A triangle has a base that is 4cm longer than its height. a. Write a polynomial that represents the area of the triangle. b. Find the area when the height is 8 cm.

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Write a polynomial that represents the area of the yard around the pool shown below. Example 4: Problem-Solving Application

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Holt McDougal Algebra 1 7-9 Special Products of Binomials List important information: The yard is a square with a side length of x + 5. The pool has side lengths of x + 2 and x – 2. 1 Understand the Problem The answer will be an expression that shows the area of the yard less the area of the pool. Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials 2 Make a Plan The area of the yard is ( x + 5) 2. The area of the pool is ( x + 2) ( x – 2). You can subtract the area of the pool from the yard to find the area of the yard surrounding the pool. Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Solve 3 Step 1 Find the total area. ( x +5) 2 = x 2 + 2( x )(5) + 5 2 Use the rule for (a + b) 2 : a = x and b = 5. Step 2 Find the area of the pool. ( x + 2)( x – 2) = x 2 – 2x + 2 x – 4 Use the rule for (a + b)(a – b): a = x and b = 2. x 2 + 10 x + 25 = x 2 – 4 = Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Step 3 Find the area of the yard around the pool. Area of yard = total area – area of pool a = x 2 + 10x + 25 (x 2 – 4)– = x 2 + 10x + 25 – x 2 + 4 = (x 2 – x 2 ) + 10x + ( 25 + 4) = 10x + 29 Identify like terms. Group like terms together The area of the yard around the pool is 10 x + 29. Example 4 Continued Solve 3

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Look Back 4 Suppose that x = 20. Then the total area in the back yard would be 25 2 or 625. The area of the pool would be 22 18 or 396. The area of the yard around the pool would be 625 – 396 = 229. According to the solution, the area of the yard around the pool is 10 x + 29. If x = 20, then 10 x +29 = 10(20) + 29 = 229. Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials To subtract a polynomial, add the opposite of each term. Remember!

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Check It Out! Example 4 Write an expression that represents the area of the swimming pool.

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Check It Out! Example 4 Continued 1 Understand the Problem The answer will be an expression that shows the area of the two rectangles combined. List important information: The upper rectangle has side lengths of 5 + x and 5 – x. The lower rectangle is a square with side length of x.

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Holt McDougal Algebra 1 7-9 Special Products of Binomials 2 Make a Plan The area of the upper rectangle is (5 + x )(5 – x ). The area of the lower square is x 2. Added together they give the total area of the pool. Check It Out! Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Solve 3 Step 1 Find the area of the upper rectangle. Step 2 Find the area of the lower square. (5 + x )(5 – x ) = 25 – 5 x + 5 x – x 2 Use the rule for (a + b) (a – b): a = 5 and b = x. – x 2 + 25= x2 x2 = = x x Check It Out! Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Step 3 Find the area of the pool. Area of pool = rectangle area + square area a x2 x2 + = –x 2 + 25 + x 2 = (x 2 – x 2 ) + 25 = 25 –x 2 + 25 = Identify like terms. Group like terms together The area of the pool is 25. Solve 3 Check It Out! Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials Look Back 4 Suppose that x = 2. Then the area of the upper rectangle would be 21. The area of the lower square would be 4. The area of the pool would be 21 + 4 = 25. According to the solution, the area of the pool is 25. Check It Out! Example 4 Continued

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Holt McDougal Algebra 1 7-9 Special Products of Binomials

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Holt McDougal Algebra 1 7-9 Special Products of Binomials 7.9 Homework: Part I Multiply. 1. ( x + 7) 2 2. ( x – 2) 2 3. (5 x + 2 y ) 2 4. (2 x – 9 y ) 2 5. (4 x + 5 y )(4 x – 5 y ) 6. ( m 2 + 2 n )( m 2 – 2 n )

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Holt McDougal Algebra 1 7-9 Special Products of Binomials 7.9 Homework: Part II 7. Write a polynomial that represents the shaded area of the figure below. x + 6 x – 6x – 7

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