how do you f o i l in maths?

Question

i know what it means
first
outer
inner
last
but i dont know how to do it

Answer 1

You have (1+2)(3+4)

First (1 & 3 are the first numbers in each bracket): 1x3=3
Outer (1 & 4 are the outer numbers): 1x4=4
Inner (2 & 3 are the inner numbers): 2x3=6
Last (2 & 4 are the last numbers): 2x4=8

Then you add the results: 3+4+6+8=21

Another example:
(x+2)(x-2)

F: x * x=x squared
O: x * 2=2x
I: 2 * x=2x
L: 2x2=-4

Then add the results: xsquared+2x+2x+(-4)= x squared+4x-4

Answer 2

well lets look at an example

to make it easy so you can understand we will do this.

(x + 1)(y + 2)

you multiply the numbers in the first parenthesis by the numbers in the second parenthesis. that means:

( x * y ) + ( x * 2 ) + ( 1 * y ) + ( 1 * 2 )

see how you take the "x" and then multiply it by each of the numbers in the second parenthesis. then you take the "1" and do the same.

you know when i was in math class this never made sense. in fact i didnt really understand this till i was out of school.

hope this helped some. =]

edit: i think beach bum did a mighty fine job of explaining it.

Answer 3

I always thought it was stupid how they explain math stuff. You just multiply each number\\

(x-8)(x+2)
xtimes x is xsquared
-8 times x is -8x
then multiply the first thing and the last thing:
x times 2 is 2x
then the second and the last
-8times 2 is -16
add like terms, and you get
xsquared -6x -16

Answer 4

when you have a binomial equation. for example:
(5x+3)(2x-1)
first: 5x times 2x = 10x (squared)
outer: 5x times -1 = -5x
inner: 3 times2x = 6x
last: 3 times -1 = -3

so your answer is: 10x(squared)-5x+6x-3
where I wrote squared, you have to put a small number 2 in the upper right hand corner. I just can't do it on this computer. good luck

Answer 5

example: (3 + 5x)(6 + 2x)
you multiple the first number in parenthisis, 3 *6
then 3 *2x (outer)
then 5x* 6 (inner)
then 5x * 2x (last)
you get the answer of 18+6x
+30x +10x
=18+36x+10x or 18+46x =D hope that helped~!

Answer 6

example of foil


(x+2)(x+4)

f x*x=x^2
o 4*x= 4x
i 2*x=2x
l 2*4=8

answer X^2+6x+8

Answer 7

(3x+5)(1-2)
3x-6x+5-10
-3x-5
x=-2
Basically you multiply the 1st terms in each parenthesis, then the outer terms, then the inner terms, then the last & solve as a regular equation.

Answer 8

(X+3)(X+1)

1) Multiply the first thing in each bracket together = X&X
= X(squared)
2) Multiply the outer thing in each bracket = X&1 = X
3) Multiply the inner thing in each bracket = 3&X = 3X
4) Multiply the last thing in each bracket = 3&1 = 3

Answer for (X+3)(X+1) = X(squared) + 4X + 3

Do you get it now?

Answer 9

(x+1)*(x+2)=x^2+3x+2

First, multiply x's
Outer multiply x and 2
Inner Multiply x and 1
Last multiply 1 and 2

Answer 10

you multiply the first two then then inner two thwn the outer two then both of the last
(0,1) (2,3) 0x2 1x2 0x3 1x3