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sharmishtha_goel
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IMO:D
Just substitute 1 and -1, in the given equation!
each sufficient!
sufficient??
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Source: Beat The GMAT — Data Sufficiency |
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Brian@VeritasPrep
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This is a pretty good question to struggle on, actually, because it helps to really figure out what Data Sufficiency is all about.
***The question is NOT asking you to solve for k***
Your job is only to answer the given question, which asks if the result of the quadratic is greater than 0. We don't need to know whether k is greater than 0, we're only concerned with whether the expression itself is greater than 0.
***"Equal to" is NOT "greater than"***
With statement 1, if you plug in 1 for k you get: 1^2 + 1 - 2 = 0. Well, 0 is not greater than 0, so we get the emphatic answer "NO" to the overall question.
***"NO" means "Sufficient"***
Because you get the definitive answer "NO" in statement 1, that is sufficient. The answer choices just deal with whether you have sufficient information to answer the question; it doesn't matter whether the answer is YES or NO - either is sufficient. The only insufficient answer is "MAYBE" (or "SOMETIMES").
So statement 1 is sufficient. Statement 2 is not - because it says k > -1, k could be 0 (which makes the whole expression equal to -2, giving the answer "NO") or k could be 1000 (which would clearly make the expression greater than 0, giving the answer "YES"). So 2 is not sufficient, 1 is sufficient, and the correct answer is A.
***The question is NOT asking you to solve for k***
Your job is only to answer the given question, which asks if the result of the quadratic is greater than 0. We don't need to know whether k is greater than 0, we're only concerned with whether the expression itself is greater than 0.
***"Equal to" is NOT "greater than"***
With statement 1, if you plug in 1 for k you get: 1^2 + 1 - 2 = 0. Well, 0 is not greater than 0, so we get the emphatic answer "NO" to the overall question.
***"NO" means "Sufficient"***
Because you get the definitive answer "NO" in statement 1, that is sufficient. The answer choices just deal with whether you have sufficient information to answer the question; it doesn't matter whether the answer is YES or NO - either is sufficient. The only insufficient answer is "MAYBE" (or "SOMETIMES").
So statement 1 is sufficient. Statement 2 is not - because it says k > -1, k could be 0 (which makes the whole expression equal to -2, giving the answer "NO") or k could be 1000 (which would clearly make the expression greater than 0, giving the answer "YES"). So 2 is not sufficient, 1 is sufficient, and the correct answer is A.
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Veritas Prep
Looking for GMAT practice questions? Try out the Veritas Prep Question Bank. Learn More.
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Gurpinder
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This is a Definitive Yes/No Question. A definitive YES OR NO will make the statement sufficient.sharmishtha_goel wrote:
Is k^2 + k -2 > 0 ?
1) k=1
2) k > -1
(1) Clearly Sufficient.
k^2 + k -2 --> 1+ (-1) = 0. Hence a definitive NO.
(2) K > -1
We don't know whether K is an integer or a fraction.
K can be { -1/2, 0, 1/2, 1}
If K = -1/2
Then.... k^2 + k -2 > 0 --> 1/4 - 3/2 = -5/4 Which is not greater than 0.
If K = 2, k^2 + k -2 --> 4 + 2-2 = 4. Which is greater than 0.
Hence insufficient.
Therefore (A)
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