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Find the quotient: ( x 3 + 5 x 2 + 8 x + 6 ) ÷ ( x + 2 ) .

x 2 + 3 x + 2 + 2 x + 2

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Find the quotient: ( 2 x 3 + 8 x 2 + x 8 ) ÷ ( x + 1 ) .

2 x 2 + 6 x 5 3 x + 1

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Look back at the dividends in [link] , [link] , and [link] . The terms were written in descending order of degrees, and there were no missing degrees. The dividend in [link] will be x 4 x 2 + 5 x 2 . It is missing an x 3 term. We will add in 0 x 3 as a placeholder.

Find the quotient: ( x 4 x 2 + 5 x 2 ) ÷ ( x + 2 ) .

Solution

Notice that there is no x 3 term in the dividend. We will add 0 x 3 as a placeholder.

A polynomial, x to the fourth power minus x squared minus 5 x minus 2, divided by another polynomial, x plus 2.
Write it as a long division problem. Be sure the dividend is in standard form with placeholders for missing terms. The long division of x to the fourth power plus 0 x cubed minus x squared minus 5 x minus 2 by x plus 2.
Divide x 4 by x .
Put the answer, x 3 , in the quotient over the x 3 term.
Multiply x 3 times x + 2. Line up the like terms.
Subtract and then bring down the next term.
x cubed is written on top of the long division bracket above the x cubed term in the dividend. Below the first two terms of the dividend x to the fourth power plus 2 x cubed is subtracted to give negative 2 x cubed minus x squared. A note next to the division reads “It may be helpful to change the signs and add.”
Divide −2 x 3 by x .
Put the answer, −2 x 2 , in the quotient over the x 2 term.
Multiply −2 x 2 times x + 1. Line up the like terms.
Subtract and bring down the next term.
x cubed minus 2 x squared is written on top of the long division bracket. At the bottom of the long division negative 2 x cubed minus 4 x squared is subtracted to give 3 x squared plus 5 x. A note reads “It may be helpful to change the signs and add.”
Divide 3 x 2 by x .
Put the answer, 3 x , in the quotient over the x term.
Multiply 3 x times x + 1. Line up the like terms.
Subtract and bring down the next term.
x cubed minus 2 x squared plus 3 x is written on top of the long division bracket. At the bottom of the long division 3 x squared plus 6 x is subtracted to give negative x minus 2. A note reads “It may be helpful to change the signs and add.”
Divide − x by x .
Put the answer, −1, in the quotient over the constant term.
Multiply −1 times x + 1. Line up the like terms.
Change the signs, add.
x cubed minus 2 x squared plus 3 x minus 1 is written on top of the long division bracket. At the bottom of the long division negative x minus 2 is subtract to give 0. A note reads “It may be helpful to change the signs and add.” The polynomial x to the fourth power minus x squared plus 5 x minus 2, divided by the binomial x plus 2 equals the polynomial x cubed minus 2 x squared plus 3 x minus 1.
To check, multiply ( x + 2 ) ( x 3 2 x 2 + 3 x 1 ) .
The result should be x 4 x 2 + 5 x 2 .

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Find the quotient: ( x 3 + 3 x + 14 ) ÷ ( x + 2 ) .

x 2 3 x + 7 x 2 2 x + 7

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Find the quotient: ( x 4 3 x 3 1000 ) ÷ ( x + 5 ) .

x 3 8 x 2 + 40 x 200

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In [link] , we will divide by 2 a 3 . As we divide we will have to consider the constants as well as the variables.

Find the quotient: ( 8 a 3 + 27 ) ÷ ( 2 a + 3 ) .

Solution

This time we will show the division all in one step. We need to add two placeholders in order to divide.

The figure shows the long division of 8 a cubed plus 27 by 2 a plus 3. In the long division bracket, placeholders 0 a squared and 0 a are added into the polynomial. On the first line under the dividend 8 a cubed plus 12 a squared is subtracted. To the right, an arrow indicates that this value came from multiplying 4 a squared by 2 a plus 3. The subtraction gives negative 12 a squared plus 0 a. From this negative 12 a squared minus 18 a is subtracted. To the right, an arrow indicates that this value came from multiplying 6 a by 2 a plus 3. The subtraction give 18 a plus 27. From this 18 a plus 27 is subtracted. To the right, an arrow indicates that this value came from multiplying 9 by 2 a plus 3. The result is 0.

To check, multiply ( 2 a + 3 ) ( 4 a 2 6 a + 9 ) .

The result should be 8 a 3 + 27 .

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Find the quotient: ( x 3 64 ) ÷ ( x 4 ) .

x 2 + 4 x + 16

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Find the quotient: ( 125 x 3 8 ) ÷ ( 5 x 2 ) .

25 x 2 + 10 x + 4

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Access these online resources for additional instruction and practice with dividing polynomials:

Key concepts

  • Fraction Addition
    • If a , b , and c are numbers where c 0 , then
      a c + b c = a + b c and a + b c = a c + b c

  • Division of a Polynomial by a Monomial
    • To divide a polynomial by a monomial, divide each term of the polynomial by the monomial.

Practice makes perfect

In the following exercises, divide each polynomial by the monomial.

42 x 2 14 x 7

6 x 2 2 x

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( 16 y 2 20 y ) ÷ 4 y

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( 55 w 2 10 w ) ÷ 5 w

11 w 2

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( 9 n 4 + 6 n 3 ) ÷ 3 n

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( 8 x 3 + 6 x 2 ) ÷ 2 x

4 x 2 + 3 x

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20 b 2 12 b −4

−5 b 2 + 3 b

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51 m 4 + 72 m 3 −3

−17 m 4 24 m 3

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310 y 4 200 y 3 5 y 2

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412 z 8 48 z 5 4 z 3

103 z 5 12 z 2

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51 y 4 + 42 y 2 3 y 2

17 y 2 + 14

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( 24 p 2 33 p ) ÷ ( −3 p )

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( 35 x 4 21 x ) ÷ ( −7 x )

−5 x 3 + 3

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( 63 m 4 42 m 3 ) ÷ ( −7 m 2 )

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( 48 y 4 24 y 3 ) ÷ ( −8 y 2 )

−6 y 2 + 3 y

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( 63 a 2 b 3 + 72 a b 4 ) ÷ ( 9 a b )

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( 45 x 3 y 4 + 60 x y 2 ) ÷ ( 5 x y )

9 x 2 y 3 + 12 y

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52 p 5 q 4 + 36 p 4 q 3 64 p 3 q 2 4 p 2 q

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49 c 2 d 2 70 c 3 d 3 35 c 2 d 4 7 c d 2

7 c 10 c 2 d 5 c d 2

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66 x 3 y 2 110 x 2 y 3 44 x 4 y 3 11 x 2 y 2

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72 r 5 s 2 + 132 r 4 s 3 96 r 3 s 5 12 r 2 s 2

6 r 3 + 11 r 2 s 8 r s 3

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12 q 2 + 3 q 1 3 q

4 q + 1 1 3 q

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10 x 2 + 5 x 4 −5 x

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20 y 2 + 12 y 1 −4 y

−5 y 3 + 1 4 y

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36 p 3 + 18 p 2 12 p 6 p 2

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63 a 3 108 a 2 + 99 a 9 a 2

7 a 12 + 11 a

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Divide a Polynomial by a Binomial

In the following exercises, divide each polynomial by the binomial.

( y 2 + 7 y + 12 ) ÷ ( y + 3 )

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( d 2 + 8 d + 12 ) ÷ ( d + 2 )

d + 6

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( x 2 3 x 10 ) ÷ ( x + 2 )

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( a 2 2 a 35 ) ÷ ( a + 5 )

a 7

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( t 2 12 t + 36 ) ÷ ( t 6 )

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( x 2 14 x + 49 ) ÷ ( x 7 )

x 7

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( 6 m 2 19 m 20 ) ÷ ( m 4 )

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( 4 x 2 17 x 15 ) ÷ ( x 5 )

4 x + 3

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( q 2 + 2 q + 20 ) ÷ ( q + 6 )

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( p 2 + 11 p + 16 ) ÷ ( p + 8 )

p + 3 8 p + 8

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( y 2 3 y 15 ) ÷ ( y 8 )

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( x 2 + 2 x 30 ) ÷ ( x 5 )

x + 7 + 5 x 5

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( 3 b 3 + b 2 + 2 ) ÷ ( b + 1 )

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( 2 n 3 10 n + 24 ) ÷ ( n + 3 )

2 n 2 6 n + 8

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( 2 y 3 6 y 36 ) ÷ ( y 3 )

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( 7 q 3 5 q 2 ) ÷ ( q 1 )

7 q 2 + 7 q + 2

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( z 3 + 1 ) ÷ ( z + 1 )

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( m 3 + 1000 ) ÷ ( m + 10 )

m 2 10 m + 100

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( a 3 125 ) ÷ ( a 5 )

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( x 3 216 ) ÷ ( x 6 )

x 2 + 6 x + 36

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( 64 x 3 27 ) ÷ ( 4 x 3 )

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( 125 y 3 64 ) ÷ ( 5 y 4 )

25 y 2 + 20 x + 16

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Everyday math

Average cost Pictures Plus produces digital albums. The company’s average cost (in dollars) to make x albums is given by the expression 7 x + 500 x .

  1. Find the quotient by dividing the numerator by the denominator.
  2. What will the average cost (in dollars) be to produce 20 albums?
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Handshakes At a company meeting, every employee shakes hands with every other employee. The number of handshakes is given by the expression n 2 n 2 , where n represents the number of employees. How many handshakes will there be if there are 10 employees at the meeting?

45

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Writing exercises

James divides 48 y + 6 by 6 this way: 48 y + 6 6 = 48 y . What is wrong with his reasoning?

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Divide 10 x 2 + x 12 2 x and explain with words how you get each term of the quotient.

Answers will vary.

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This is a table that has three rows and four columns. In the first row, which is a header row, the cells read from left to right “I can…,” “Confidently,” “With some help,” and “No-I don’t get it!” The first column below “I can…” reads “divide a polynomial by a monomial,” and “divide a polynomial by a binomial.” The rest of the cells are blank.

After reviewing this checklist, what will you do to become confident for all goals?

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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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