inertia2010 wrote:Can someone please explain this?
x is a positive integer divisible by 4; as x increases from 1824 to 1896, which of the following must decrease?
I. 4x2 - 4x + 4
II. -10 - 1/x2
III. 4/x2
A) I only
B) II only
C) III only
D) II and III only
E) None
Thanks!
Only two conditions matter: x must be a positive integer, and the value of x must increase. Ignore the other conditions. The question becomes:
If x is a positive integer, as the value of x increases, which of the following must decrease?
Plug in x=1 and x=2.
Eliminate answers that do not decrease.
I. 4x2 - 4x + 4
If x=1, 4x*2 - 4x + 4 = 4.
If x=2, 4x^2 - 4x + 4 = 12.
The value of x increases from 4 to 12.
Eliminate any answer choice that includes I.
Eliminate A.
II. -10 - 1/x^2
If x=1, -10 - 1/x^2 = -11.
If x=2, -10 - 1/x^2 = -10.25.
The value of x increases from -11 to -10.25.
Eliminate any answer choice that includes II.
Eliminate B and D.
III. 4/x^2
If x=1, 4/x^2 = 4.
If x=2, 4/x^2 = 1.
The value of x decreases from 4 to 1.
The correct answer must include III.
Eliminate E.
The correct answer is
C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
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.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
