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Can you explain the F.O.I.L method to me

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paulbarton | Honors

Posted June 21, 2012 at 2:16 AM via web

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Can you explain the F.O.I.L method to me

Tagged with f.o.i.l method, math

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted June 21, 2012 at 5:43 AM (Answer #1)

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The FOIL method is used to multiply two binomials. FOIL stands for First, Outer, Inner, Last

If the product (a + b)(c + d) has to be determined, using FOIL:

First : a*c

Outer: a*d

Inner: b*c

Last: b*d

Adding a*c, a*d, b*c and b*d the product is (a + b)(c + d) = a*c + a*d + b*c + b*d

Sources:

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etotheeyepi | Student , Undergraduate | Valedictorian

Posted June 21, 2012 at 3:26 AM (Answer #2)

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FOIL stands for first, outer, inner, and last.

It's a way to organize finding the product of 

(a + b) (c+d)

The first is ac.  The outer is ad.  The inner is bc.  The last is bd.

So, (a + b) (c+d) = ac + ad + bc +bd.

Often the outer and inner terms are like terms, and the product has three terms instead of four.

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jerichorayel | College Teacher | (Level 1) Senior Educator

Posted June 21, 2012 at 5:45 AM (Answer #3)

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Let me show you an example of foil method

(a + b ) (c + d)  = ac + ad + bc + bd

(x + 2) (x + 5)   =  (x)(x)  + (5)(x) + (2)(x) + (5)(2)

                         = x^2 + 5x + 2x + 10 -------> combine like terms

                         = x^2 + 7x + 10

 

(X + 5) (2X-3) = (X)(2X) + (X)(-3) + (5)(2X) + (5)(-3)

                      = 2X^2 + (-3X) + (10X) + (-15) --> Notice the sign

                      = 2x^2 -3x + 10x -15  -->combine like terms

                      = 2x^2 +7x -15

 

(2x - 2)(5x - 2)  = (2X)(X) + (2X)(-2) + (-2)(5X) + (-2)(-2)

                        = 2X^2 + (-4X) + (-10X) + (4)

                        = 2X^2 -4X - 10X + 4

                        2X^2  - 14X + 4

hope this helps :)

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