Introduction: How to FOIL
FOIL is an acronym used in mathematics which stands for Firsts Outers Inners Lasts. It is a process used to multiply polynomials of two terms together. A polynomial is a sum of terms, and a term is just a constant (any number) multiplied by a variable (some unknown number). An example of a polynomial would be 5x + 2, where 5x and 2 are the terms of the polynomial. FOILing is a fundamental mathematical skill used throughout algebra, calculus, and other high level math courses.
In order to complete this process, you should be able to add multiply.
You will need:
- Two polynomials consisting of two terms to multiply
It typically takes around 3 minutes to complete this process.
In this example we will multiply together two simple polynomials, x+1 and x+2.
Step 1: Firsts
Start by multiplying the first term of each polynomial together. In this case the first term for each is x, so we will multiply x times x.
Step 2: Outers
Next, we will multiply the terms on the outside of the two polynomials. In this case, an x and a 2 are on the outside, so we multiply x times 2.
Step 3: Inners
Now we will multiply the terms on the inside (1 and x).
Step 4: Lasts
Lastly, we will multiply the last term of each polynomial together to obtain 1 times 2 equals 2.
Step 5: Add Terms Together
Add the terms we obtained together to get our answer.
Step 6: Simplify
Now we want to add like terms together to obtain the simplest answer possible. In this case we will add 2x and x together to obtain 3x.
We were able to add 2x and x (notice: x = 1*x) together because both terms are a number multiplied by x. We could not have added x and 3 together because 3 does not have an x attached to it.
Step 7: Conclusion
You have now successfully multiplied two polynomials together to obtain a new polynomial by FOILing.
If you found this Instructable interesting, you might also enjoy:
- Factoring: https://www.instructables.com/id/How-to-factor/
- Multiplying fractions: https://www.instructables.com/id/Multiplying-Fract...
- Graphing: https://www.instructables.com/id/How-to-Graph/
Khan Academy also has many helpful math videos on its YouTube channel: https://www.youtube.com/user/khanacademy