xy =1
(2^(x+y)^2)/(2^(x-Y)^2)

now we will use one concept which say that a^b/a^c=a^(b-c)
so we can reduce the given problem to 2 ^(((x+y)^2)-((x-y)^2))
2^(x^2+y^2+2xy -(x^2+y^2 - 2xy)) as we know (a+b)^2=a^2+b^2+2ab and (a-b)^2=a^2+b^2-2ab
2^(4xy) since remaining term will cancel out
2^(4*1)
2^4=16

amising6 wrote:xy =1
(2^(x+y)^2)/(2^(x-Y)^2)

now we will use one concept which say that a^b/a^c=a^(b-c)
so we can reduce the given problem to 2 ^(((x+y)^2)-((x-y)^2))
2^(x^2+y^2+2xy -(x^2+y^2 - 2xy)) as we know (a+b)^2=a^2+b^2+2ab and (a-b)^2=a^2+b^2-2ab
2^(4xy) since remaining term will cancel out
2^(4*1)
2^4=16

Thanks Amising6
Actually, I knew the rule, but I dont' know why I get blocked during the exam with a timer !!.
Silvia