If xy = 1, what is the value of 2^[(x+y)^2] / 2^[(x-y)^2] ?
(A) 2
(B) 4
(C) 8
(D) 16
(E) 32
ans: D
PP-T1-28
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由 aqboy[origen] » 2008-03-07 01:47
2^[(x+y)^2] / 2^[(x-y)^2]
=2^[(x+y)^2-(x-y)^2]
=2^[x^2+2xy+y^2-x^2+2xy-y^2]
=2^[4xy]
=2^4
=16
ans:D
=2^[(x+y)^2-(x-y)^2]
=2^[x^2+2xy+y^2-x^2+2xy-y^2]
=2^[4xy]
=2^4
=16
ans:D
- aqboy[origen]
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