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Problem solving math question
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GMATGuruNY
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x² - 2x - 3 = 0Which of the following expressions CANNOT be equal to 0 when x² − 2x = 3?
A. x² − 6x + 9
B. x² − 4x + 3
C. x² − x − 2
D. x² − 7x + 6
E. x² − 9
(x-3)(x+1) = 0
x=3 or x=-1.
Eliminate any answer choice that CAN be equal to 0 when x=3 or x=-1.
A wise test-taker knows the following:
When the question stem includes the phrase which of the following, the correct answer is likely to be D or E.
E: x² − 9
If we plug x=3 into x² − 9, we get:
3² − 9 = 0.
Eliminate E.
D: x² − 7x + 6
If we plug x=3 into x² − 7x + 6, we get:
3² − 7*3 + 6 = -6.
If we plug x=-1 into x² − 7x + 6, we get:
(-1)² − 7(-1) + 6 = 14.
x² − 7x + 6 cannot be equal to 0 when x=3 or x=-1.
The correct answer is D.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
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Thanks Mitch, much appreciated for the detailed explanation!
Could you explain what you mean by "When the question stem includes the phrase which of the following, the correct answer is likely to be D or E"?
Is this something that likely pattern of return on the real GMAT test?
Could you explain what you mean by "When the question stem includes the phrase which of the following, the correct answer is likely to be D or E"?
Is this something that likely pattern of return on the real GMAT test?
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GMATGuruNY
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Which of the following blah, blah, blah?vinhaha wrote:Thanks Mitch, much appreciated for the detailed explanation!
Could you explain what you mean by "When the question stem includes the phrase which of the following, the correct answer is likely to be D or E"?
Is this something that likely pattern of return on the real GMAT test?
The goal of the test-writer is to induce us to waste time.
Here, the average test-taker will start with A.
For this reason, the correct answer is likely to be D or E, inducing the average test-taker to waste time testing three or four incorrect answer choices.
Thus:
When the question stem includes the phrase which of the following, start with E and work your way up.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
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Brent@GMATPrepNow
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ASIDE: Whenever a question requires you to INSPECT each answer choice (as is the case with this question), the GMAT test-makers love to put the correct answer near the bottom.
So, in these situations, I always suggest that students start at answer choice E and work their way up to A.
Cheers,
Brent
So, in these situations, I always suggest that students start at answer choice E and work their way up to A.
Cheers,
Brent
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Matt@VeritasPrep
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Seconded!Brent@GMATPrepNow wrote:ASIDE: Whenever a question requires you to INSPECT each answer choice (as is the case with this question), the GMAT test-makers love to put the correct answer near the bottom.
So, in these situations, I always suggest that students start at answer choice E and work their way up to A.
Cheers,
Brent
Incidentally, this also applies to Sentence Correction problems in which the whole sentence is underlined.
