Last visit was: 15 Sep 2026, 04:08 It is currently 15 Sep 2026, 04:08
Home
Messages
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
User avatar
anirban16
User avatar
Joined: 24 Jan 2005
Last visit: 20 Jun 2005
Posts: 141
Own Kudos:
73
 [4]
Location: Boston
Posts: 141
Kudos: 73
 [4]
If x be real, find the maximum value of the expression -2x^2 18 Mar 2005, 15:18
2
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

55% (hard)

Question Stats:

66% (02:06) correct 34% (02:00) wrong based on 135 sessions

History

Date
Time
Result
Not Attempted Yet
If x be real, find the maximum value of the expression -2x^2 + x + 3

(A) 2.145
(B) 3.125
(C) 1.725
(D) 1.885
(E) 3.485

Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
ShowHide Answer
Official Answer
B
User avatar
kapslock
User avatar
Joined: 15 Mar 2005
Last visit: 19 Mar 2007
Posts: 202
Own Kudos:
71
 [1]
Location: Phoenix
Posts: 202
Kudos: 71
 [1]
If x be real, find the maximum value of the expression -2x^2 18 Mar 2005, 16:19
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
anirban16
If x be real, find the maximum value of the expression -2x^2 + x + 3

(a) 2.145
(b) 3.125
(c) 1.725
(d) 1.885
(e) 3.485
Show more


(B) 3.125.

differentiate the expression to get x = 1/4.

substitute x = 1/4 in the expression to get 3.125.

There's a way to know this value is the maxima or the minima, by double differentiation and substituting the value. Can't remember precisely. Can someone please explain?

Thanks.
User avatar
banerjeea_98
User avatar
Joined: 18 Nov 2004
Last visit: 17 May 2012
Posts: 674
Own Kudos:
202
Posts: 674
Kudos: 202
If x be real, find the maximum value of the expression -2x^2 18 Mar 2005, 16:28
Kudos
Add Kudos
Bookmarks
Bookmark this Post
"B"

Differentiate the eq
-4x+1 = 0
x = 1/4

-1/8+ 1/4+3 = (-1+2)/8 + 3 = 1/8 + 3 = 25/8 = 3.125
avatar
PareshGmat
avatar
Joined: 27 Dec 2012
Last visit: 10 Jul 2016
Posts: 1,531
Own Kudos:
8,439
Given Kudos: 193
Status:The Best Or Nothing
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Posts: 1,531
Kudos: 8,439
If x be real, find the maximum value of the expression -2x^2 05 Mar 2014, 03:35
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel, can you please tell if this is a GMAT question??
User avatar
Edvento
User avatar
Joined: 08 Apr 2012
Last visit: 06 Jul 2014
Posts: 95
Own Kudos:
249
Given Kudos: 14
Posts: 95
Kudos: 249
If x be real, find the maximum value of the expression -2x^2 Updated on: 05 Mar 2014, 06:52
Originally posted by Edvento on 05 Mar 2014, 04:42.
Last edited by Edvento on 05 Mar 2014, 06:52, edited 1 time in total.
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Guys,

This is quite a tough GMAT question.

Solution:

-2x^2 + x + 3 = -( 2x^2 - 3x +2x - 3) = -{x(2x - 3) +(2x - 3)} = (x +1)(3 - 2x)

The graph of the quadratic expression is of the form shown in the figure attached. It is a symmetric graph that intersects the x axis at -1 and 3/2.

Due to it's symmetric nature, the maxima can be obtained at 1/4, the average of -1 and 3/2.

So the maxima will be obtained at x = 1/4.
Attachments

Quant_Problem.jpg
Quant_Problem.jpg [ 18.86 KiB | Viewed 5379 times ]

User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 15 Sep 2026
Posts: 113,519
Own Kudos:
841,374
Given Kudos: 111,537
Products:
GMAT Club Tests
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 113,519
Kudos: 841,374
If x be real, find the maximum value of the expression -2x^2 05 Mar 2014, 05:19
Kudos
Add Kudos
Bookmarks
Bookmark this Post
PareshGmat
Bunuel, can you please tell if this is a GMAT question??
Show more

It could be. Check:
what-is-the-minimum-value-of-the-function-y-x-2-4x-126302.html
a-quadratic-function-f-x-attains-a-max-of-3-at-x-1-the-87703.html

Also read last chapter of our book on Coordinate Geometry: math-coordinate-geometry-87652.html

Hope it helps.

Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
Moderator:
Bunuel
Math Expert
113521 posts