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 Question from Subrahmanya:

n1, n2, n3....................,n1997 are integers not necessarily distinct. (actually in n1, n2,.............., n1997 the numbers 1,2,.................,1997 are subscripts of 'n')

X= (-1)^n1+(-1)^n2+............+(-1)^n998

Y=(-1)^n999+(-1)^n1000+............+(-1)^n1997

Then

which of the following options is true

A) (-1)^X = 1, (-1)^Y = 1 B) (-1)^X = 1, (-1)^Y = -1
C) (-1)^X = -1, (-1)^Y = 1 D) (-1)^X = -1, (-1)^Y = -1
E) none of these

Hi,

I have a suggestion that I hope will point you in the right direction.

let $k$ be the number of integers in $n_1, n_2, n_3, \cdot \cdot \cdot , n_{998}$ that are even.

Penny

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