Multiplying Binomials

The FOIL Method

FOIL: What does it mean?

• F: First

• O: Outer

• I: Inner

• L: Last

EXAMPLE: Multiply (x + 3)(x + 2)

F: x * x = x2 I: 3*x = 3x

O: x * 2 = 2x L: 3*2 = 6

So we have x2 + 2x + 3x + 6 or x2 + 5x + 6

Now You Try!

Multiply (x – 1)(x + 4)

HINT: When you multiply using the 1, think of it as a -1!

Let’s Check your work!

(x – 1)(x + 4)F: x*x = x2

O: x*4 = 4xI: -1*x = -1xL: -1*4 = -4

Put it all together! x2 + 4x – 1x – 4 orx2 + 3x - 4

Let’s try a word problem!

EXAMPLE: What is the area of a pool whose width is x + 2 and whose length is four more than its width

First, we need to realize that to find area we multiply length times width. Also, since the length is four more than x + 2, then the length is x + 2 + 4 or x + 6

Let’s Try a Word Problem!

Now we need to multiply them together!

(x +2)(x + 6)

Using our foil method we get:

X2 + 6x + 2x + 12

Or x2 + 8x + 12