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We're going to need this for the next lesson. 

We'll need to multiply guys like

( 7 - sqrt(2) )( 5 + sqrt(3) )

There's an easy process we can use called FOIL.

F=First
O=Outer
I=Inner
L=Last

You can use this process anytime you multiply two things that are added or subtracted inside of two sets of parentheses.  Boy, that sounds confusing!  Like this:

( a + b )( c + d ) = ac + ad + bc + bd