OG DS-Algebra Question

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OG DS-Algebra Question

by aaggar7 » Sun Mar 03, 2013 9:54 pm
Hi,
I request your help to find the answer for the below question.

What is the value of integer n ?
(1) n ( n + 1) = 6
(2) 2^2n = 16

1 is definitely not sufficient.
2 Since 2^2n = 16 this can be rewritten as 2^2n = 2^4 or 2^2n = (-2)^4 in the later case we cannot equate the left hand side and the right hand side,so I think the answer should be E
But as per OG solution the correct answer is B.

Can anyone please clarify where I am going wrong.
Source: — Data Sufficiency |

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by Anurag@Gurome » Sun Mar 03, 2013 9:58 pm
aaggar7 wrote:2 Since 2^2n = 16 this can be rewritten as 2^2n = 2^4 or 2^2n = (-2)^4 in the later case we cannot equate the left hand side and the right hand side...
it is given that 2^2n.
You cannot just change the base to -2.
aaggar7 wrote:What is the value of integer n ?
(1) n ( n + 1) = 6
(2) 2^2n = 16
Statement 1: This means the product of two consecutive integers n and (n + 1) is 6. One obvious such pair is 2 and 3, i.e. n = 2. But -2, and -3, i.e. n = -3 is also another possibility.

Not sufficient

Statement 2: 16 can be expressed as a power of 2 in only one way which is 2^4.
Hence, 2n = 4 ---> n = 2

Sufficient

The correct answer is B.
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