Factoring Trinomials - "Fred is better" ...

[MIch elle]

says my dh. My older ds is having trouble factoring trinomials and I gave dh 2 algebra books, Elementary Algebra, Larson and Life of Fred Beg. Algebra, and DH said "Fred is better." He said, Fred explains it faster and easier than Larson. I gave dh these 2 algebra books because we own them & have the answers to all the problems in both books.

 

My ds is using neither of these books for his high school, but we don't have all the answers to that book. So to help ds, my dh read LOF and is now explaining factoring trinomials.

[Jann in TX]

I have a method that helps the students think through the factoring steps. Things are fairly easy to 'see' until you put a co-efficient in front of the squared term!

 

If you--or anyone else would like the lessons just e-mail me and I'll send them right out.

 

The method is self-checking too! I've never had a student who could not factor trinomials. A big thanks to my 8th grade math teacher--who learned it from a former ESL student during her student teaching.

 

Jann

 

PS-I bet LOF is a great resource for concepts like this--I have yet to see a traditional math text make this simple factoring concept understandable! I usually have my students IGNORE (as in cover up--do not look at) their texts for this section and just look at my lessons.

[MIch elle]

I'll ask today and see if they any need further help. :D

[Laurie in CA]

I use Chalkdust and Mr. Mosely did not show this method but it is in the text.

Shortcut method for factoring trinomials (this beats trial and error)

I would teach the student the trial/error method first and they will really appreciate this shortcut.

Also called factoring by grouping:

6x^2-11x-10

Step 1

Multiply the leading coefficient by the last coefficient

6 times 10 equals 60

Step 2

Rewrite trinomial with 2 blanks in the middle

6x^2_____ ______ -10

Step 3

Find factors of 60 where the difference will equal the middle term (-11x)

6 and 10 (no)

30 and 2 (no)

and other factors until you find the right combination

15 and 4 (yes)

Step 4

Put factors in blanks

6x^2-15x+4x-10

or

6x^2+4x-15x-10

Both of these will factor correctly

Step 5

Factor by grouping the first 2 together and the last 2 together

2x(3x+2)-5(3x+2)

Step 6

(2x-5) (3x+2)

 

Step 3 will be different depending on the signs but it is pretty easy to figure that out + +, you will need the sum of the 2 factors, - + , you need the sum of 2 negative factors, + -, like the example shown, you need the difference.