Questions about the world of GMAT Math from other sources and general math related questions.
themarkac
 
 

First and Second Degree Equations

by themarkac Fri Mar 14, 2008 10:48 pm

From OG DS #67

[question deleted because it is from a banned source - please remember that GMAC has requested that OG questions NOT be posted online anywhere, including our site]



My question is what is the rule that allows you to create take simplify the equation from a(b+c) + d(b+c) to (a+d) + (b+c)???
KTsincere
 
 

by KTsincere Mon Mar 17, 2008 5:09 pm

First: In your question you asked how can A(B+C) + D(B+C) = (A+D) + (B+C)... You made a typo it should read =(A+D)(B+C) There is no addition sign between (A+D) and (B+C)... its multiplication.

If you foil (A+D)(B+C) --> AB + AC +DB + DC ... this is the orignal equation just in a different order

OR if you don't like to "FOIL" try this method

you could use the vics method and assign each letter a value (A=2, B=3, C=4, D=5):
A(B+C) + D(B+C) --> 2(3+4) + 5(3+4) = 2(7)+5(7) = 14+35 =49
(A+D)(B+C) --> (2+5) (3+4) = (7)(7) = 49

Hope this helps.

KT