Sak32 wrote:What is the value of integer n?

1) n(n+1) = 6
2) 2^(2n) = 16

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Target question: What is the value of integer n?

Statement 1: n(n+1) = 6
Expand to get: n² + n = 6
Set equal to zero: n² + n - 6 = 0
Factor: (n + 3)(n - 2) = 0
So, n = -3 or n = 2
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: 2^(2n) = 16
2^(2n) = 16
Rewrite 16 as 2^4 to get: 2^(2n) = 2^4
So, we can conclude that (2n) = 4, in which case n must equal 2
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = B

Cheers,
Brent

Sak32 wrote: What is baffling me is that in 2) the answer should be Not Sufficient because logically it could be either 2 or -2. Why didnt we consider the -2 as well?? Both powers yield 16 since they are even. The answer was deemed sufficient with 2 only.

Let's try n = 2 and n = -2

n = 2: 2^(2n) = 2^(4) = 16 PERFECT
n = -2: 2^(2n) = 2^(-4) = 1/16 nope

I believe that you're thinking of a different rule that refers to situations in which the BASE (not the exponent) is negative.

So for example, 4^2 = 16 and (-4)^2 = 16

Cheers,
Brent