GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Oct 2019, 00:11 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

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.  For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Director  V
Joined: 18 Feb 2019
Posts: 581
Location: India
GMAT 1: 460 Q42 V13 GPA: 3.6
For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

3 00:00

Difficulty:   65% (hard)

Question Stats: 50% (01:49) correct 50% (01:52) wrong based on 82 sessions

HideShow timer Statistics

For what value of x between -5 and 1 inclusive, the value of 6x^2–x^4-4 is greatest?

A. -5
B. -√5
C. -2
D. -√3
E. 1
Manager  G
Joined: 21 Feb 2019
Posts: 125
Location: Italy
Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

2
I differentiated:

$$12x - 4x^3 = 0$$

$$x^3 - 3x = 0$$

$$x(x^2 - 3) = 0$$

$$x = {0, +\sqrt{3}, -\sqrt{3}}$$

Since there is only $$-\sqrt{3}$$ among the options, pick it up.

_________________
If you like my post, Kudos are appreciated! Thank you.

MEMENTO AUDERE SEMPER
Manager  G
Joined: 14 May 2018
Posts: 96
Location: India
Concentration: Finance, Entrepreneurship
GMAT 1: 710 Q49 V38 GPA: 4
Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

kiran120680 wrote:
For what value of x between -5 and 1 inclusive, the value of 6x^2–x^4-4 is greatest?

A. -5
B. -√5
C. -2
D. -√3
E. 1

if we use -5,it will give a very large negative value, so cancel it. the larger the value,the more negative it will keep getting. just check for -\sqrt{3} and 1.

Ans:D
_________________
Please hit kudos if you like my answers.

GMAT:710 (Q49,V38,IR8,AWA5)
Director  V
Joined: 18 Feb 2019
Posts: 581
Location: India
GMAT 1: 460 Q42 V13 GPA: 3.6
Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

lucajava wrote:
I differentiated:

$$12x - 4x^3 = 0$$

$$x^3 - 3x = 0$$

$$x(x^2 - 3) = 0$$

$$x = {0, +\sqrt{3}, -\sqrt{3}}$$

Since there is only $$-\sqrt{3}$$ among the options, pick it up.

Can you please explain elaborately
Manager  G
Joined: 21 Feb 2019
Posts: 125
Location: Italy
Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

1
kiran120680 wrote:
lucajava wrote:
I differentiated:

$$12x - 4x^3 = 0$$

$$x^3 - 3x = 0$$

$$x(x^2 - 3) = 0$$

$$x = {0, +\sqrt{3}, -\sqrt{3}}$$

Since there is only $$-\sqrt{3}$$ among the options, pick it up.

Can you please explain elaborately

In math, the first derivative is used to find max. and min. values of a function. Starting from this point, i differentiated to find the $$x$$ where the function takes the greatest value. Hope it's clear.
_________________
If you like my post, Kudos are appreciated! Thank you.

MEMENTO AUDERE SEMPER
LBS Moderator D
Joined: 04 Jun 2018
Posts: 646
Location: Germany
Concentration: General Management, Finance
GMAT 1: 730 Q47 V44 GPA: 3.4
WE: Analyst (Transportation)
Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4  [#permalink]

Show Tags

Can someone provide the actual algebraic way to this question?
_________________ Re: For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4   [#permalink] 13 May 2019, 10:33
Display posts from previous: Sort by

For what value of x between -5 and 1 inclusive, the value of 6x^2-x^4

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  