PLS HELP :IN GMAT, IS ZERO A POSITIVE INTEGER : ??

[himu]

My Q :
PLS HELP : IS ZERO A POSITIVE INTEGER : ??? Whats the thumb rule, I am a bit confused over this.
If Yes then ans D, below,is okay otherwise B cannot be eliminated.
Can anyone pls clarify more on the following Q ?
Thanks for your time

If x is a positive integer, which of the following CANNOT be expressed as n^2, where n is an integer?

A. x^5
B. x^2 − 1
C. Sqrt(X^8)
D. x^2 + 1
E. Sqrt(X^5)


[spoiler]D. For each of choices A, B, C, and E, trying the value x = 1 shows that there is one possible value of x for which the expression results in an integer squared:

A) The result is 1, which is the same thing as
12

B) The result is 0, which is the same thing as
02

C) The result is 1, which is the same thing as
12

E) The results is 1, which is the same thing as
12

For D, however, you cannot find a value of x for which
x2+1
will yield a perfect square. If x = 1, the expression yields a 2. If x = 2, the expression yields a 5. As no two squares (other than 0 and 1) are one number apart, D cannot be a perfect square if x is a positive integer.[/spoiler]

[Brent@GMATPrepNow]

If x is a positive integer, which of the following CANNOT be expressed as n^2, where n is an integer?

A. x^5
B. x^2 − 1
C. Sqrt(X^8)
D. x^2 + 1
E. Sqrt(X^5)

[/spoiler]

To answer your question, zero is not a positive integer. Zero is neither positive or negative.



To answer the given question, we'll eliminate 4 answer choices by providing an instance in which the answer choice CAN be expressed as n^2, where n is an integer.

A. x^5
If x = 1, then x^5 = 1, and 1 can be written as 1^2
ELIMINATE A

B. x^2 - 1
If x = 1, then x^2 - 1 = 0, and 0 can be written as 0^2
ELIMINATE B

C. Sqrt(X^8)
If x = 1, then sqrt(x^8) = sqrt(1) = 1, and 1 can be written as 1^2
ELIMINATE C

D. x^2 + 1
Can't think of a counter-example, so I'll leave answer choice D for the moment.

E. sqrt(X^5)
If x = 1, then sqrt(x^5) = sqrt(1) = 1, and 1 can be written as 1^2
ELIMINATE E

Now that we've eliminated A, B, C and E, the correct answer must be D

Cheers,
Brent

[faraz_jeddah]

0 is neither +ve nor -ve.

But it is still an EVEN integer.