PP-T1-28

[yiyiyi]

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

[aqboy[origen]]

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