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Algebra

by Tagne » Mon Mar 14, 2011 1:00 pm
1. If two of the expressions x+y, x+5y, x-y, and 5x-y are chosen at random, what is the probability that their product will be of the form of x2 - (by)2, where b is an integer?
a. ½
b. 1/3
c. /4
d. 1/5
e. 1/6

please note x2 = x square and (by)2 = by square
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by force5 » Mon Mar 14, 2011 1:14 pm
IMO - E ( 1/6)

4 expressions can multiply with each other (without repeating combination) in 6 ways

only one way ( x+y) *(x-y) will yield you desired result ( in the form x^2-(by)^2
(x+y)*(x-y) = x^2-y^2 ( here b can be considered 1)


hope that helps
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