if two of the four expression x+y, x+5y , x-y and x-5y are chosen at random, what is the probability that their product will be of the form of x^2 - (by)^2 , where b is integer?
1. 1/2
2. 1/3
3. 1/4
4. 1/5
5. 1/6
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g.shankaran
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cans
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(x+y)(x-y) and (x+5y)(x-5y) are 2 such pairs
total=4C2=6
thus prob=2/6=1/3
IMO B
total=4C2=6
thus prob=2/6=1/3
IMO B
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