Math A

Creative Factoring of Trinomials

 

Looking for a creative way to encourage students to factor trinomials?  Consider the following process.

Please direct questions on this process to Vivian Donnelly.

When teaching students to factor   ax2+bx+c,
consider using the following method:

1.  The first step is to set up the following:  

2.  Find two factors of ac that have a sum of b.

3.  Call these factors f 1 and f 2.  Place them as shown: 

4.  Check to see if there is anything that can be factored out of the
     parentheses in each of the 2 sets.

5.  Reduce the fraction, if possible.

 

Example:

Factor: 

step 1: 

step 2:   find two factors of ac with a sum of b
              find two factors of (24)(6)=144 with a sum of 25 --> 16 & 9

step 3:   

step 4:  factor each set of parentheses
             
(24x + 16 ) = 8( 3x + 2)    and    (24x + 9) = 3(8x + 3)

              which means you have

step 5:  reduce if possible.
              this leaves you with
( 3x + 2 )( 8x + 3 )

 

For some students this process may be much easier than making a long list of possible solutions to "guess and check". It makes factoring a leading coefficient of say 24, just as easy to do as a leading coefficient of 1!

This also helps students to fully factor a trinomial, since any constant would be factored out and left separated from the remaining factors.

 

 
 

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Roberts