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23 Sep 2018, 21:52
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
84% (01:04) correct
16%
(01:13)
wrong
based on 1285
sessions
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Date
Time
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Not Attempted Yet
What is the value of 5x^2 + 4x - 1 ?
(1) x(x + 2) = 0
(2) x = 0
(1) x(x + 2) = 0
(2) x = 0
Pure algebraic questions like this one are no longer part of the GMAT Data Sufficiency syllabus.
For relevant Data Sufficiency questions, please check the Data Sufficiency forum:
Data Sufficiency Forum
Data Sufficiency Forum
23 Sep 2018, 22:34
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Bunuel
\(5x^2+4x-1\)
\(=5x^2+5x-x-1\)
\(=5x(x+1)-1(x+1)\)
\(=(x+1)(5x-1)\)
Statement 1: x(x + 2) = 0
Either x=0 or x=-2
If x=0,
\(5x^2+4x-1=(+1)(-1)=-1\)
If x=-2
\(5x^2+4x-1=(-2+1)(-10-1)=(-1)(-11)=11\)
Insufficient
Statement 2: x = 0
It will lead to a single value of expression as seen above.
Sufficient.
Answer: B
NOTE: In the case of first statement, it is absolutely necessary to check the value of the expression for any two given values of x.
Since quadratics represent a parabola on a XY plane, there will be 2 values of X for any given value of the quadratic expression(except the lowest or the highest value).
Question makers can trick test takers into this trap.
04 Nov 2019, 12:58
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How do we get x=0 from statement 1? Didn’t understand.
Posted from my mobile device
Posted from my mobile device
