# 6.4 Multiplying/Dividing Polynomials 1/10/2014. How do you multiply 1256 by 13?

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6.4 Multiplying/Dividing Polynomials 1/10/2014

How do you multiply 1256 by 13?

Example 1 Multiply Polynomials Vertically Find the product. () x 2x 2 4x4x7 – + () 2x – SOLUTION Line up like terms vertically. Then multiply as shown below. x 2x 2 4x4x7 – + 2x – × 2x 22x 2 8x8x+14 –– Multiply by 2. x 2x 2 4x4x7 – + – x 3x 3 7x7x+ – 4x 24x 2 Multiply by x. x 2x 2 4x4x7 – + x 3x 3 15x+ – 2x 22x 2 +14 Combine like terms.

Example 2 Multiply Polynomials Horizontally Find the product. () 4+3x3x () 5x 25x 2 x6 – + a. 4+3x3x () 5x 25x 2 x6 – + () 5x 25x 2 x6 – + = Use distributive property. SOLUTION () 4+3x3x () 5x 25x 2 x6 – + a. + 15x 3 18x – +20x 2 4x4x24 – + = 3x 23x 2 Use distributive property. 15x 3 + 24 – = 20x 2 3x 23x 2 + 18x4x4x – + Group like terms. 15x 3 14x – + = 23x 2 24 – Combine like terms.

Example 2 Multiply Polynomials Horizontally () 2x – () x 2x 2 2x2x3 – + = b. () 2x – () 1x – () 3x + + x 3x 3 3x3x – +2x 22x 2 4x4x6 – = 2x 22x 2 – Use distributive property. x 3x 3 + 6 = 2x 22x 2 2x 22x 2 3x3x4x4x – – – + Group like terms. + x 3x 3 7x7x – 6 = Combine like terms. 2x – () x 2x 2 2x2x3 – + = () x 2x 2 2x2x3 – + Multiply any 2 binomials Multiply by the 3 rd binomial

Checkpoint Multiply Polynomials Find the product. Use either a horizontal or vertical format. 1. () 1+x () x 2x 2 x2++ 2. () 2x 22x 2 x4 – + () 3x – ANSWER 2x 22x 2 3x3x2x 3x 3 +++ 7x 27x 2 7x7x122x 32x 3 + ––

Checkpoint Multiply Polynomials Find the product. Use either a horizontal or vertical format. 3. () 1+2x2x () 3x 23x 2 x1 – + ANSWER 5x 25x 2 x16x 36x 3 + –– x 2x 2 10x8x 3x 3 + – + () 1x – 4. () 4x + () 2x –

Checkpoint Use Special Product Patterns Find the product. () 7z – () 7z + 5. ANSWER z 2z 2 49 – 6. ()2)2 23y3y + 12y9y 29y 2 4++ ANSWER 64x 3 + – 12x48x 2 – 1 ANSWER 7. – ()3)3 14x4x

Homework: Worksheet 6.4

6.4 Multiplying/Dividing Polynomials….cont’d. 1/29/2014

Example 4 Use Long Division Find the quotient 985 23. ÷ Divide 98 by 23. 985 23 -92 Subtract the product. 4 () 23 = 92 65 Bring down 5. Divide 65 by 23. 19 Remainder ANSWER The result is written as. 23 19 42 -46 Subtract the product. 2 () 23 = 46 42

Example 5 Use Polynomial Long Division Find the quotient. () 4x + x 3x 3 + – 6x6x 3x 23x 2 – 4 () ÷ Write division in the same format you use to divide whole numbers. x 3x 3 +4x 24x 2 Subtract the product. () 4x + x 2x 2 = x 3x 3 4x 24x 2 + – 6x6xx 2x 2 – Bring down - 6x. Divide –x 2 by x – 4x4xx 2x 2 – Subtract the product. () 4x + x = x 2x 2 4x4x ––– – 2x2x – 4 Bring down - 4. Divide -2x by x 4 Remainder x 3x 3 + – 6x6x3x 23x 2 – 4x+4 x 3x 3 ÷x = x 2x 2 ANSWER The result is written as. x 2x 2 –– x2 x+4 4 + – 2x2x – 8 Subtract the product () 4x + 2 = 2x2x8 –––. x2x2 -x -2 - +

Example 5 Use Polynomial Long Division CHECKYou can check the result of a division problem by multiplying the divisor by the quotient and adding the remainder. The result should be the dividend (what’s inside ). +4x 2x 2 –– x2 () x+4 () = x+4 () x 2x 2 – xx+4 () – 2x+4 () +4 = x 3x 3 –– 4x4x+44x 24x 2 x 2x 2 + – 2x2x – 8 = x 3x 3 – 6x6x3x 23x 2 + – 4

Synthetic division: Is a method of dividing polynomials by an expression of the form x - k

Example 1 Using Synthetic division x – (-4) in x – k form -4Coefficients of powers of x 1 3 -6 -4 k 1 -4 4 multiply -2 8 4 add coefficients of the power of x in descending order, starting with the power that is one less than that of the dividend. ANSWER x 2x 2 –– x2 x+4 4 + remainder

Example 2 Using Synthetic division 3 Coefficients of powers of x 2 -7 0 6 -14 k 2 6 -3 multiply -3 -9 -23 add remainder -3 -9 ANSWER

Checkpoint Find the quotient. 5x5x4x 34x 3 + () +1x ( +1 ) ÷ ANSWER 4x4x4x24x2 + – 9+ x+1 8 –

Example 3 Use Polynomial Long Division Can’t use synthetic division because it isn’t being divided by x-k - + remainder

Example 3 Use Polynomial Long Division Can’t use synthetic division because it isn’t being divided by x-k - + - remainder

Homework: WS: Dividing Polynomials

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