Question 1592: I dont understand how to use the "FOIL" method. Can you help me out?
Answer by AnlytcPhil(1806)   (Show Source):
You can put this solution on YOUR website! I dont understand how to use the "FOIL" method. Can you help me out?
`
FOIL is acronym for Firsts, Outers, Inners, Lasts.
`
We use the "FOIL" method when we have a binomial times a binomial:
`
(A + B)(C + D)
`
The A is the FIRST term in the left binomial
The C is the FIRST term in the right binomial
The B is the LAST term in the left binomial
The D is the LAST term in the right binomial
A and D are the two OUTER terms, because they are on the outside,
` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` ` i.e., the fartherest apart
`
B and C are the two INNER terms, because they are on the inside.
`
"FOIL" reminds us to
F. Multiply the two FIRST terms together, getting AC
O. Multiply the two OUTER terms together, getting AD
I. Multiply the two INNER terms together, getting BC
L. Multiply the two LAST terms together, getting BD
`
So (A + B)(C + D) = AC + AD + BC + CD
`
Three examples:
`
(7a + 3b)(5c + 2d) =
`
(7a)(5c) + (7a)(2d) + (3b)(5c) + (3b)(2d) =
`
35ac + 14ad + 15bc + 6bd
`
----------------------------------
`
(2x + 3)(6x + 5) =
`
(2x)(6x) + (2x)(5) + (3)(6x) + (3)(5) =
`
12x² + 10x + 18x + 15 =
`
12x² + 28x + 15
`
-------------------------------------------------------
`
(4s - 7)(8s + 3) =
`
(4s)(8s) + (3)(4s) + (-7)(8s) + (-7)(3) =
`
32s² + 12s - 56s - 21 =
`
32s² - 44s - 21
`
Edwin
|
|
|
