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Trinomials - Undoing FOIL

( -2 ) ( 6 ) = -12 and -2 + 6 = 4 or ( 2 ) ( -6 ) = -12 and +2 - 6 = -4 ...the second option is correct

 

So,    x^2- 4x - 12 = ( x + 2 ) ( x - 6 )

 

YOUR TURN:

Factory^2 + 8y + 15 = ( y 3 ) ( y )
Factorx^2 - x - 90 = ( x ) ( x 10 )

Now, let's work from scratch!

Factor     x^2 - 6x + 5

We start with

( x ) ( x )

Our last term is 5... our only choice is

1 * 5

The 5 has to be positive...

( -1 ) ( -5 ) = 5 or ( 1 ) ( 5 ) = 5 ... the middle guy is -6 ... -1 - 5 = -6 ... therefore, it is the first option

So,    x^2 - 6x + 5 = ( x - 1 ) ( x - 5 )

That one was pretty easy since 5 is prime.