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18 Dec 2018, 01:27
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
45% (01:45) correct
55%
(01:54)
wrong
based on 154
sessions
History
Date
Time
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What is the value of z if z is not positive ?
(1) |x-2| + |x+y-5| + |x+y+z| = 0
(2) z^3 – 25z = 0
(1) |x-2| + |x+y-5| + |x+y+z| = 0
(2) z^3 – 25z = 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
18 Dec 2018, 01:38
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What is the value of z if z is not positive ?
(1) |x-2| + |x+y-5| + |x+y+z| = 0
Absolute value is always non-negative, so the above to be true all three terms must be 0 (the sum of non-negative terms to be 0, all the terms must be 0).
x + y - 5 = 0, thus x + y = 5.
x + y + z = 0. Since from above, x + y = 5, then 5 + z = 0 --> z = -5.
Sufficient.
(2) z^3 – 25z = 0.
z(z^2 - 25) = 0.
z = 0 or z = -5 or z = 5. Given that z is not positive, we are left with z = 0 or z = -5. Not sufficient.
Answer: A.
(1) |x-2| + |x+y-5| + |x+y+z| = 0
Absolute value is always non-negative, so the above to be true all three terms must be 0 (the sum of non-negative terms to be 0, all the terms must be 0).
x + y - 5 = 0, thus x + y = 5.
x + y + z = 0. Since from above, x + y = 5, then 5 + z = 0 --> z = -5.
Sufficient.
(2) z^3 – 25z = 0.
z(z^2 - 25) = 0.
z = 0 or z = -5 or z = 5. Given that z is not positive, we are left with z = 0 or z = -5. Not sufficient.
Answer: A.
24 Jan 2019, 10:39
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I tried to solve second equation this way:
z^3-25z=0
z^3=25z
z^2=25
z= +/-5
Since z is not positive it must be -5 then.
can anyone please correct me where i am going wrong.
z^3-25z=0
z^3=25z
z^2=25
z= +/-5
Since z is not positive it must be -5 then.
can anyone please correct me where i am going wrong.
