F.O.I.L

The F.O.I.L formula is used for multiplying polynomials. The letters stand for:

F: first

O: outside

I: inside

L: last

For example:

(y + 1) (y + 3)

You would take the First numbers in each bracket, which are both y, and multiply them together, which gives y2

Then you would take the Outside number in each bracket, and multiply them together

(y + 1) (y + 3) = y2 + 3y

Next you take the Inside numbers in the brackets, and multiply those two numbers

(y + 1) (y + 3) = y2 + 3y + 1y

Finally you take the Last two numbers in the brackets, and multiply them

(y + 1) (y + 3) = y2 + 3y+ 1y +3

For the final answer you must combine the like terms,

(y + 1) (y + 3) = y2 + 4y + 3

Another example:

(2x - 3) (x + 5)

F: 2x2

O: +10x

I: -3x

L: -15

(2x - 3) (x + 5) = 2x2 + 7x - 15

A common mistake that often occurs when using F.O.I. L. is that when you get to the last term, many people often ADD instead of multiplying. Be careful not to make this mistake!

~ By Jessica S.

 
Math Projects

Mathematics | Science | Worsley School

All content by students
Bill Willis 2000
Wunderland Website Design