A Math Forum Web Unit

Suzanne Alejandre's

Understanding Algebraic Factoring

Main Activity

Back to Suzanne's Math Lessons || Check out Suzanne's Tessellation Lessons

Main Activity:

1. Introduce the algebra tiles.

   What shape is this? Answer: (square)

   What shape is this? Answer: (rectangle)

   How long is this side? Answer: (x units)

   How long is this side? Answer: (1 unit)

   Before continuing, make certain that it is clear that you are working with pieces that are one of the following:

   one unit square
   one rectangle that is one unit wide and "x" units long.
   one square that is "x" units long by "x" units wide.

2. Using algebra tiles, show that
   (x + 1)(x + 3)

   can be shown using the tiles:

   

   Rearrange the tiles so that they look like this:

   

   What is that?

   It is

   one square that is "x" units long by "x" units wide
   four rectangles that are one unit wide and "x" units long, and
   3 unit squares

   which can also be written as:

   

3. Now have students try:
   (x+4)(x+2)

   (x+5)(x+1)

   etc.

Once the students have an understanding of what algebraic factoring really is, introducing the FOIL method will have more meaning.