vtrang82 wrote:If k does not equal -1,0 or 1, does 1 / k > 0?
I. 1 / (K+1) >0
II. 1 / (K-1) >0
My approach to this question is to pick strategic numbers to substitute k, ie. -2, -0.5 , 0.5 and 2.
The question really asks whether k is positive or negative.
I. If k+1 > 0 ---> k could be -0.5, 0.5 or 2. non-sufficient
II. If k-1 > 0 ---> k could be -0.5 or 2. non sufficient
I. and II. together ---> k could be -0.5 or 2. non-sufficient
Thus my answer would be E.
Yet it seems that the answer is A.
Why?
Thank you for your time.
You've miscopied the question. The two statements are given in reverse order. Here's the correct question:
If k is not equal to 0, 1, or -1, is 1/k>0?
(1) 1/(k-1)>0
(2) 1/(k+1)>0
Here's the approach that I would use:
In order for 1/k to be positive, k must be positive. Rewritten, the question is asking:
Is k>0?
Statement 1: 1/(k-1)>0
Since the numerator of this fraction (1) is positive, the denominator (k-1) must also be positive; otherwise, the fraction will take on a negative value. Thus, statement 1 tells us that k-1>0.
k-1>0
k>1
Thus, k>0. Sufficient.
Statement 2: 1/(k+1)>0
Since the numerator of this fraction (1) is positive, the denominator (k+1) must also be positive; otherwise, the fraction will take on a negative value. Thus, statement 2 tells us that k+1>0.
k+1>0
k>-1
Thus, k could be negative (k= -1/2, for example), or k could be positive (k=1, for example). Insufficient.
The correct answer is A.
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