Question 8961: I am having trouble with FOIL, and was wondering if you could tell me how to get the answer to (9a-7)(9a + 7)
Thanks,
Kyle Pruden Answer by longjonsilver(2297) (Show Source):
Why spend time learning something like that when all you need know is what the hell you are supposed to be doing in the first place?
Right then:
you have 2 brackets
each bracket has 2 terms in it
each of the 2 terms in the first bracket needs to be multiplies with each of the 2 terms in the second bracket. Period!
As to the order you do this, it does not matter one jot! However, most people seem to take the first 9a and multiply it to the 2 terms in the second bracket and then take the second term (the -7) and multiply it to the 2 terms in the second bracket too.
So we end up with 4 terms, namely --> written out long-windedly. This becomes:
