The answer is 2x^2 -9x + 4 but I dont know how to arrive at this answer, could some one please walk me through this .
The best help you can receive with FOIL is to forget it and simply learn to multiply.
You have two factors: (2x-1) and (x-4)
Each factor has two terms.
(2x-1) has '2x' and '-1'
(x-4) has 'x' and '-4'.
Multiply each term from each factor with each term from the other factor. Keep track so you don't miss any and don't do any twice.
"FOIL" is a cute idea to keep track of 2x2 multiplication. If you learn to keep track yourself, you never need to think about it again.
Distribute the 2x and -1 from the first binomial over the second binomial, combine like terms and voila!:
I didn't know this method FOIL ^^
By the way, I'd suggest you doing this way... :
You will get
Using the basics of multiplication expanding, this is equal to :
Substituting back :
Using again this expansion :
Edit : masters of rapidity... :P