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Trinomials - Undoing FOIL

Do you remember FOIL?

Prove it by multiplying these:

( x - 5 ) ( x + 2 ) =

( x + 3 ) ( x + 3 ) =

( x - 6 ) ( x - 7 ) =

( x + 8 ) ( x + 1 ) =

OK, now we'll be undoing FOIL. I'm going to merge you into this slowly. Factoring can be a bit of a shock.

Remember that, when you do FOIL, there are inner and outer terms... This will be the key to nailing these things.

Let's try to factoring this guy:

x^2 - 4x -45

I'm going to start you out...

First, we can do the x guys -- they're easy:

( x ) ( x )

And I'm going to give you the last guys:

( x 5 ) ( x 9 )