2.01   Factoring by Sum and Difference of Cubes

Intermediate Algebra: One Step at a Time 

Pages 126 - 130:   #2, 10, 11, 18, 24, 28, 30, 32, 33, 34

Dr. Robert J. Rapalje

Seminole State College of Florida

Sanford, FL  32773

 

To see Section 2.01, with explanations, examples, exercises, and answers, click here!

 

 

Guidelines to Factoring

 

  1. Common Factor
  2. Trinomials
  3. Difference of Squares; Difference and Sum of Cubes
  4. Grouping

 

 

p. 127.  # 2.        

Solution: 

Next, notice that this is a difference of two cubes!  The  FIRST is  and the SECOND is which can be written  .  Remember also that the difference of two cubes factors into the product of a binomial times a trinomial in this form, according to the formula

What you have is:

        

                     

    

  

 

The trinomial CANNOT be factored, so this is your final answer!!

p. 127.  # 10.        

Next, notice that this is a difference of two cubes!  The  FIRST is  which can be written  and the SECOND is which can be written  .  Remember also that the difference of two cubes factors into the product of a binomial times a trinomial in this form, according to the formula

What you have is:

        

                     

    

  

 

The trinomial CANNOT be factored, so this is your final answer!!

 

p. 127.  # 11.        

Next, notice that this is a sum of two cubes!  The  FIRST is  which can be written and the SECOND is which can be written  .  Remember also that the sum of two cubes factors into the product of a binomial times a trinomial in this form, according to the formula

What you have is:

        

                     

    

  

 

The trinomial CANNOT be factored, so this is your final answer!!

                                                                            

p. 128.  # 18.        

Solution: 

The first step is to recognize that there is a common factor.  Take out the 3 that is common to both terms.

                              

Next, notice that what is left the parentheses is a difference of two cubes!  The  FIRST is  and the SECOND is which can be written  .  Remember also that the difference of two cubes factors into the product of a binomial times a trinomial in this form, according to the formula

What you have is:

                               

                                

                                

The trinomial CANNOT be factored, so again this is your final answer!!

 

p. 128.  # 24.   

Next, notice that this is a SUM of two cubes!  The  FIRST is  , which is actually and the SECOND is which can be written  .  Remember  that the sum of two cubes factors into the product of a binomial times a trinomial in this form, according to the formula

What you have is:

                                       

                                               

                             

                        

 

p. 130.  # 28.        

Solution:   

The first step is to recognize that there is a common factor.  Take out the 5 and the x factor that are common to both terms.

                               

Next, notice that what is left the parentheses is a difference of two cubes! 

The  FIRST is  which can be written as  and

the SECOND is which can be written  . 

Remember also that the difference of two cubes is a binomial times a trinomial according to the formula

What you have is:

                              

                               

                               

                               

 

p. 130.  # 30.        

Solution:   

As always, the first step is to recognize that there is a common factor.  Take out the 25 and the  factor that are common to both terms.

                               

Next, notice that what is left the parentheses is a sum of two cubes! 

The  FIRST is  which can be written as  and

the SECOND is which can be written  . 

Remember also that the sum of two cubes is a binomial times a trinomial according to the formula

What you have is:

                              

                               

                               

                               

p. 130.  # 32.        

Solution: 

In this case, there are NO common factors.  So, try a trinomial.  Notice that there are three terms, so it IS a trinomial, which can be factored into the product of two binomials.

                                   

                             

                              

Notice that each of these binomials are actually differences of two cubes, and each factors:

      

 

p. 130.  # 34.        

Solution: 

This problem is easiest to factor as a difference of two squares:

                                        

                             

                              

Notice that each of these binomials are actually difference and also sum of two cubes:

You finish it:

      

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Dr. Robert J. Rapalje Altamonte Springs Campus
Contact me at:   rapaljer@seminolestate.edu
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