# Algebra/Trinomials

Trinomials are a special kind of algebraic equation that looks like this: x²+4x+4=0

There are two main things you can do with trinomials: create them and factor them.

Creating trinomials

If you have the following expressions, you can multiply them into a trinomial following the FOIL method. The letters all stand for something different:

First Outer Inner Last

This is the method that I learned last year and it always works well for me. For more help, you may email me at isabellamasters@hotmail.com. Here is how to do the foil method:

(x+6)(x+5)

Multiply the first term in each expression. x*x=x² Multiply the outer terms. x*5=5x. Multiply the inner terms. 6*x=6x. Multiply the last terms. 6*5=30

Now take all that (hope you had it written down) and add it all together like this:

x²+5x+6x+30

Since 5x and 6x both are like terms, because they both are of the same degree of x, we can add them together to get 11x.Do NOT add 5x and x², you can never, ever do that!

Factoring Trinomials You can factor trinomials by basically taking everything we just did and doing it backwards. I'll show you.

x²+13x+42

You have to find two integers that multiply up to 42 and add up to 13. What about 2 and 21? Multiplies up to 42, but together, you come up with 23. What about 6 and 7? That works! So then you just write it like before:

(x+6)(x+7)

Now let's try another, but a bit different:

(x+2)(x-1)

This one has a negative, but it isn't much harder. You should get:

x2+2x-x-2