How to Use FOIL
By: Sam C
Expanding Quadratic Equations
This is a quadratic equation in factored form. If you are asked to expand it, it can sound like a daunting task. But, not to worry. There is an easy method to expand an equation like this.
Let's use the earlier example of a factored quadratic equation to demonstrate FOIL!
F is for First- Take the first numbers in each set of parentheses and multiply them together. x x= x^2 O is for Outer- Multiply the outermost numbers of the parentheses together. 2x 3=6x
Steps 3 & 4 of FOIL
I is for Inner- Multiply the two inner numbers of the parentheses together. 5 x=5x L is for Last Multiply the last numbers of the parentheses together. 5 3=15
Bringing it all together-
Now you have four numbers: x^2, 6x, 5x, and 15. Add the 6x and the 5x together to make 11x, and add the numbers together. x^2 + 11x + 15 Now you understand FOIL!