LaVonne C.

asked • 04/08/14

how can i tell when to use the foil method?

whats the difference between foiling and distributing? 

3 Answers By Expert Tutors

By:

Dave F. answered • 04/08/14

Tutor
New to Wyzant

Math and Excel Tutor - elementary school up to middle school subjects

Steve S. answered • 04/08/14

Tutor
5 (3)

Tutoring in Precalculus, Trig, and Differential Calculus

Kay G.

Your foil one IS distribution.  This gives the impression that foil is something besides distribution.
Report

04/08/14

Parviz F.

I just avoid FOIL all together, it is just useless memorization of irrelevance:
 
 Multiply 2 binomial
 
   ( X + a ) ( X +b)
 
    Just distribute it twice:
    
   ( X +a) X + b( X +a) = X ^2 + aX + bX + ab
 
      Then factor by Grouping:
 
         X^2 + ( a + b ) X + ab
       
      Then it comes useful in factoring Quadratic and solving for roots
 
  f( X) =  X ^2 + ( a + b ) X + ab = ( X +a ) ( X +b )  
     
     f( x ) = 0   ( X +a ) = 0   X1 = -a     ( X +b) = 0   X2 = -b
 
         Substituting back ( X, X2 ) into f( X)
 
      f( X) = X^2 - ( X1 + X 2 ) X + X1X2     (2)
 
     Equation (2) leads  us to solution of roots of quadratic.
 
          Where aX^2 + bX + c = 0
 
                   always   X1 + X2 = - b/a   X1 . X2= c/a (3)
 
            Relationship ( 3) is the key Principle that leads to the solution of quadratic and even polynomial'
 
            that should be emphasized instead of FOIL.
        
 
       
 
       
 
     
Report

04/08/14

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.