How do you F.O.I.L. in algebra?

Question

This is basically the only thing holding me back in my math class. I just need a set of steps that I can apply to each problem or a simple explanation on what it means and how you do it. I think I remember it standing for First Inside Outside Last but that doesn't really help any.

Thanks!

Answer 1

u got the abbreviations ... heres what it means ...its used for polynomials...

lets say they give you this and say foil it (3x-2) (2x+4)

use the method like this

First = the first in each set ...(--> 3x ....) (-->2x..)

those get multiplied ....= 6x SQUARED(meaning its a quadratic)...you put 6x SQUARED on the side to use later ....6xSQUARED will be the beginning of your equation because you start with the largest exponent and go down......for example a random equation (nothing to do with what im showing u) would go like this,
4xcubed-5xsquared+5x+3 .....you see how the exponent gets smaller as you go to the right ?

so far...you have 6xsquared to start off the equation you're trying to make NEXT.... is the outter

Outter = the (3x) from the first one because its on the outside and the (4) from the second set bc its on the outside too...you multiply those......(3x) times (4)= 12x

put 12x on the side of your paper because you're going to get another number with an x with one of the last two steps ( the I and the L from FOIL) and you'll add it to 12x for the next part of your equation

Inner is next
you take the part from each set thats most closest to the inside
the (-2) and the (2x) are the inners
you multiply those ....= - 4x

now put the -4x on the side with the other stuff u got

now we're on LAST ...
you take the last numbers from each set...we read from left to right in america...so you go to the first set and the last part is
-2 and the second set's last part is 4

you multiply those
(-2) (4)= -8


now put the -8 on the side with the other things you had earlier


now you're ready to make an equation!

you have the 6xsquared which is all ready b/c we didnt get any other answers from the FOIL process with a SQUARED

you have two numbers with x's by them(the ones you put on the side from the FOIL part)...those will get added because they're the same ..

so 12x + -4x = 8x

so now you have nothing else with an x by itself ...so you're done with that part ...

so now you have 6xsquared and 8x

you also had a number on the side earlier(from FOIL) that was just a -8...


now you put them in order like i showed you the one with the biggest exponent goes first from left to right ...

you have 6xsquared +8x -8
THATS YOUR EQUATION! (answer)...

theres a plus sign infront of the 8x because 8x was positive
there's a negative sign infront of the 8 because we got a negative 8...so the signs in between depend on whether the numbers negative or positive when you come up with them. its not too hard...it becomes more easy if you practice more...do like 10 problems and itll be sooooooo easy bc its natural...like walking and babies...the more they do it the easier it becomes. goodluck!

Answer 2

OK

You have the concept - now let's show an example so you understand:

(x+1) (x +3) = ?? ; Using FOIL (First items, Outside items, Inside items, Last items)

x*x + x*3+ 1*x + 1*3 =
x^2 + 4x + 3

Try another
(2x -3)(x +5)
2x*x + 2x*5 - 3*x - 15
2x^2 + 7x -15

Got it? Hope that helps.

Answer 3

I don`t really think about F.O.I.L. as such.
Consider the example:-
(x + 3) (2x + 5)
My thinking is:-
(i) Multiply everything in 2nd bracket by x
(ii) Multiply everything in 2nd bracket by 3
(iii) Gather similar terms

As follows:-
2x² + 5x + 6x + 15
2x² + 11x + 15

Never a FOIL in sight!!

Answer 4

FIRST-OUTSIDE-INSIDE-LAST
thats the meaning of each letter...

just dont remember the meaning and yo'll know the answer:

like this---

(1+2)(3+4)

the anwer is.......2+4+6+8

then combined......the final answer is 20!


that's so easy man.....

Answer 5

(x+2) (x+5)

x*x = x^2
x*5=5x
2*x=2x
2*5=10

x^2+5x+2x+10=x^2+7x+10

Answer 6

say you have (a+b) times (c+d)
F.irst
O.uter
I.nner
l.ast
sou you multiply the first terms then the outer terms then the ineer terms then the last ones and add up all the products so
(a+b)(c+d) is ac+ad+bc+bd

Answer 7

I hope this helps you...I was lousy in Algebra and we didn't have the internet to search for help on.
I feel your pain.