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Given a sum of cubes or difference of cubes, factor it.

  1. Confirm that the first and last term are cubes, a 3 + b 3 or a 3 b 3 .
  2. For a sum of cubes, write the factored form as ( a + b ) ( a 2 a b + b 2 ) . For a difference of cubes, write the factored form as ( a b ) ( a 2 + a b + b 2 ) .

Factoring a sum of cubes

Factor x 3 + 512.

Notice that x 3 and 512 are cubes because 8 3 = 512. Rewrite the sum of cubes as ( x + 8 ) ( x 2 8 x + 64 ) .

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Factor the sum of cubes: 216 a 3 + b 3 .

( 6 a + b ) ( 36 a 2 −6 a b + b 2 )

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Factoring a difference of cubes

Factor 8 x 3 125.

Notice that 8 x 3 and 125 are cubes because 8 x 3 = ( 2 x ) 3 and 125 = 5 3 . Write the difference of cubes as ( 2 x 5 ) ( 4 x 2 + 10 x + 25 ) .

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Factor the difference of cubes: 1,000 x 3 1.

( 10 x 1 ) ( 100 x 2 + 10 x + 1 )

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Factoring expressions with fractional or negative exponents

Expressions with fractional or negative exponents can be factored by pulling out a GCF. Look for the variable or exponent that is common to each term of the expression and pull out that variable or exponent raised to the lowest power. These expressions follow the same factoring rules as those with integer exponents. For instance, 2 x 1 4 + 5 x 3 4 can be factored by pulling out x 1 4 and being rewritten as x 1 4 ( 2 + 5 x 1 2 ) .

Factoring an expression with fractional or negative exponents

Factor 3 x ( x + 2 ) −1 3 + 4 ( x + 2 ) 2 3 .

Factor out the term with the lowest value of the exponent. In this case, that would be ( x + 2 ) 1 3 .

( x + 2 ) 1 3 ( 3 x + 4 ( x + 2 ) ) Factor out the GCF . ( x + 2 ) 1 3 ( 3 x + 4 x + 8 ) Simplify . ( x + 2 ) 1 3 ( 7 x + 8 )
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Factor 2 ( 5 a 1 ) 3 4 + 7 a ( 5 a 1 ) 1 4 .

( 5 a −1 ) 1 4 ( 17 a −2 )

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Access these online resources for additional instruction and practice with factoring polynomials.

Key equations

difference of squares a 2 b 2 = ( a + b ) ( a b )
perfect square trinomial a 2 + 2 a b + b 2 = ( a + b ) 2
sum of cubes a 3 + b 3 = ( a + b ) ( a 2 a b + b 2 )
difference of cubes a 3 b 3 = ( a b ) ( a 2 + a b + b 2 )
  • The greatest common factor, or GCF, can be factored out of a polynomial. Checking for a GCF should be the first step in any factoring problem. See [link] .
  • Trinomials with leading coefficient 1 can be factored by finding numbers that have a product of the third term and a sum of the second term. See [link] .
  • Trinomials can be factored using a process called factoring by grouping. See [link] .
  • Perfect square trinomials and the difference of squares are special products and can be factored using equations. See [link] and [link] .
  • The sum of cubes and the difference of cubes can be factored using equations. See [link] and [link] .
  • Polynomials containing fractional and negative exponents can be factored by pulling out a GCF. See [link] .

Verbal

If the terms of a polynomial do not have a GCF, does that mean it is not factorable? Explain.

The terms of a polynomial do not have to have a common factor for the entire polynomial to be factorable. For example, 4 x 2 and −9 y 2 don’t have a common factor, but the whole polynomial is still factorable: 4 x 2 −9 y 2 = ( 2 x + 3 y ) ( 2 x −3 y ) .

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A polynomial is factorable, but it is not a perfect square trinomial or a difference of two squares. Can you factor the polynomial without finding the GCF?

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How do you factor by grouping?

Divide the x term into the sum of two terms, factor each portion of the expression separately, and then factor out the GCF of the entire expression.

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Algebraic

For the following exercises, find the greatest common factor.

14 x + 4 x y 18 x y 2

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49 m b 2 35 m 2 b a + 77 m a 2

7 m

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30 x 3 y 45 x 2 y 2 + 135 x y 3

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200 p 3 m 3 30 p 2 m 3 + 40 m 3

10 m 3

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36 j 4 k 2 18 j 3 k 3 + 54 j 2 k 4

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6 y 4 2 y 3 + 3 y 2 y

y

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For the following exercises, factor by grouping.

2 a 2 + 9 a 18

( 2 a −3 ) ( a + 6 )

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6 n 2 19 n 11

( 3 n −11 ) ( 2 n + 1 )

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2 p 2 5 p 7

( p + 1 ) ( 2 p −7 )

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For the following exercises, factor the polynomial.

10 h 2 9 h 9

( 5 h + 3 ) ( 2 h −3 )

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9 d 2 −73 d + 8

( 9 d −1 ) ( d −8 )

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12 t 2 + t 13

( 12 t + 13 ) ( t −1 )

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16 x 2 100

( 4 x + 10 ) ( 4 x 10 )

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121 p 2 169

( 11 p + 13 ) ( 11 p 13 )

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361 d 2 81

( 19 d + 9 ) ( 19 d 9 )

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144 b 2 25 c 2

( 12 b + 5 c ) ( 12 b 5 c )

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49 n 2 + 168 n + 144

( 7 n + 12 ) 2

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225 y 2 + 120 y + 16

( 15 y + 4 ) 2

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m 2 20 m + 100

( 5 p 12 ) 2

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For the following exercises, factor the polynomials.

x 3 + 216

( x + 6 ) ( x 2 6 x + 36 )

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125 a 3 + 343

( 5 a + 7 ) ( 25 a 2 35 a + 49 )

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64 x 3 −125

( 4 x 5 ) ( 16 x 2 + 20 x + 25 )

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125 r 3 + 1,728 s 3

( 5 r + 12 s ) ( 25 r 2 60 r s + 144 s 2 )

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4 x ( x 1 ) 2 3 + 3 ( x 1 ) 1 3

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3 c ( 2 c + 3 ) 1 4 5 ( 2 c + 3 ) 3 4

( 2 c + 3 ) 1 4 ( −7 c 15 )

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3 t ( 10 t + 3 ) 1 3 + 7 ( 10 t + 3 ) 4 3

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14 x ( x + 2 ) 2 5 + 5 ( x + 2 ) 3 5

( x + 2 ) 2 5 ( 19 x + 10 )

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9 y ( 3 y 13 ) 1 5 2 ( 3 y 13 ) 6 5

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5 z ( 2 z 9 ) 3 2 + 11 ( 2 z 9 ) 1 2

( 2 z 9 ) 3 2 ( 27 z 99 )

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6 d ( 2 d + 3 ) 1 6 + 5 ( 2 d + 3 ) 5 6

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Real-world applications

For the following exercises, consider this scenario:

Charlotte has appointed a chairperson to lead a city beautification project. The first act is to install statues and fountains in one of the city’s parks. The park is a rectangle with an area of 98 x 2 + 105 x 27 m 2 , as shown in the figure below. The length and width of the park are perfect factors of the area.

A rectangle that’s textured to look like a field. The field is labeled: l times w = ninety-eight times x squared plus one hundred five times x minus twenty-seven.

Factor by grouping to find the length and width of the park.

( 14 x −3 ) ( 7 x + 9 )

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A statue is to be placed in the center of the park. The area of the base of the statue is 4 x 2 + 12 x + 9 m 2 . Factor the area to find the lengths of the sides of the statue.

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At the northwest corner of the park, the city is going to install a fountain. The area of the base of the fountain is 9 x 2 25 m 2 . Factor the area to find the lengths of the sides of the fountain.

( 3 x + 5 ) ( 3 x −5 )

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For the following exercise, consider the following scenario:

A school is installing a flagpole in the central plaza. The plaza is a square with side length 100 yd. as shown in the figure below. The flagpole will take up a square plot with area x 2 6 x + 9 yd 2 .

A square that’s textured to look like a field with a missing piece in the shape of a square in the center. The sides of the larger square are labeled: 100 yards. The center square is labeled: Area: x squared minus six times x plus nine.

Find the length of the base of the flagpole by factoring.

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Extensions

For the following exercises, factor the polynomials completely.

16 x 4 200 x 2 + 625

( 2 x + 5 ) 2 ( 2 x 5 ) 2

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16 z 4 2,401 a 4

( 4 z 2 + 49 a 2 ) ( 2 z + 7 a ) ( 2 z 7 a )

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5 x ( 3 x + 2 ) 2 4 + ( 12 x + 8 ) 3 2

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( 32 x 3 + 48 x 2 162 x 243 ) −1

1 ( 4 x + 9 ) ( 4 x −9 ) ( 2 x + 3 )

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Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, College algebra. OpenStax CNX. Feb 06, 2015 Download for free at https://legacy.cnx.org/content/col11759/1.3
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