Wednesday, October 11, 2017

Middle School Math Solutions – Expand Calculator, FOIL Method

In our last blog post we covered the distributive law. In this blog post, we will focus on an application of the distributive law, the FOIL method.

The FOIL method is used when multiplying two binomials together. Quick reminder: a binomial is an expression of the sum or difference of two terms.

The FOIL method is when we take the sum of the first two terms multiplied together, the outer terms multiplied together, the inner terms multiplied together, and the last terms multiplied together. This is where we get the acronym FOIL (first, outer, inner last).

Let’s visualize this and see it in a formula:


Let’s see some examples now, using the FOIL method.

First example (click here):

                                                                 (x+3)(x+1)

1.  Use the FOIL method

Remember, we want the sum of the first terms multiplied together, the outer terms multiplied together, the inner terms multiplied together, and the last terms multiplied together.
2.  Simplify

                                                     (x+3)(x+1)=x∙x+x∙1+3∙x+3∙1

                                                                  =x^2+x+3x+3

                                                                    =x^2+4x+3

   Multiply terms and add like terms

Not, too complicated. Let’s see two more examples.

Next example (click here):

                                                                    (2x+1)(x-1)

1. Use the FOIL method


2. Simplify

                                                        (2x+1)(x-1)=2x^2-2x+x-1

                                                                     =2x^2-x-1

Last example (click here):

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

1. Use the FOIL method


2. Simplify

                                             (3x^2+y)(-x+5y)=-3x^3+15x^2 y-xy+5y^2

As you can see, multiplying binomials using the FOIL method isn’t hard. The FOIL method is so helpful throughout your math courses, so it is important to memorize and get the hang of it. Once you start practicing, this will become second nature to you. For practice problems or more help on the FOIL method, check out our Practice.

Until next time,

Leah

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