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by pradeepkaushal9518 » Fri Oct 01, 2010 4:11 am
If p is a positive integer, is p2 - 1 divisible by 4?

p = 2n + 3, where n is an integer.
p + 1 is divisible by 3.
A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.
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by shovan85 » Fri Oct 01, 2010 4:26 am
IMO A

p2 is P^2 right!!

Only 1 has the correct n whether +ve or -ve or zero. All satisfies p^2 - 1. (Suff)
By 2 we will have p as 2, 5, 8... if u take 2 it does not satisfy
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by sumit.sinha » Fri Oct 01, 2010 4:28 am
pradeepkaushal9518 wrote:If p is a positive integer, is p2 - 1 divisible by 4?

p = 2n + 3, where n is an integer.
p + 1 is divisible by 3.
A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.
IMO A

(p-1)(p+1) will be divisible by 4 iff p is odd i..e (p-1) and (p+1) will be multiples of 2.
is p odd?
(1) p -3 = even integer
so p is odd. Sufficient.
(2) p can be 2 ( which is even) or can be 5(which is odd) Insufficient

A.
Cheers,
Sumit
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