# Thread: If n and x are positive

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## If n and x are positive

. If n and x are positive integers, is n^x+2n divisible by 3?
(1) x=3
(2) n=5

SPOILER:

i think Official Answer must be E cause :
from statement 1 we have? n3+2n
if we check 1,2,4,5,6,... for n ,it would be divisable by 3 but if we check 3 it would be 27+6=31 and it is not divisable bye 3 ,so can not get a certain answer to us ,thus it must be E

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Originally Posted by mehrak
. If n and x are positive integers, is n^x+2n divisible by 3?
(1) x=3
(2) n=5
SPOILER:

i think Official Answer must be E cause :
from statement 1 we have? n3+2n
if we check 1,2,4,5,6,... for n ,it would be divisable by 3 but if we check 3 it would be 27+6=31 and it is not divisable bye 3 ,so can not get a certain answer to us ,thus it must be E
Hmm 27 + 6 = 33 . This is where it troubled you.

So , it is A

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Originally Posted by Retake_GMAT
Hmm 27 + 6 = 33 . This is where it troubled you.

So , it is A
ohhhh my God!!!! I made a foolish mistake!!! tanx retake gmat!

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Stmt 1: n^3+2n= n(n^2+2) = n(n^2-1+3) = n(n+1)(n-1) +3n
So it is divisible by 3.

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Though one can get the answer by plugging numbers ecartman explained it beautifully why we get the result...

Any number not divisile by 3,when squared and added with 2 will be divisible by 3.

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i got A too
n^3+2n = n(n^2+2)=n(n^2 -1 +3)=n((n-1)(n+1)+3)
so n^3+2n divisible by 3

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