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

 It is currently 23 Oct 2019, 09:06 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.  M03-18

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

Hide Tags

Intern  B
Joined: 18 Jan 2018
Posts: 38
Location: India
Concentration: Finance, Marketing
GPA: 3.98

Show Tags

Bunuel in this question, I took x = (x^2) and hence calculated the roots for (x^2)^2-2(x^2)+1 by the formula root(B^2-4ac) which turned out to be 0 and hence, I marked choice B. Am I missing something?
Math Expert V
Joined: 02 Sep 2009
Posts: 58465

Show Tags

aalakshaya wrote:
Bunuel in this question, I took x = (x^2) and hence calculated the roots for (x^2)^2-2(x^2)+1 by the formula root(B^2-4ac) which turned out to be 0 and hence, I marked choice B. Am I missing something?

$$(x^2)^2-2(x^2)+1 =0$$

$$x^2=\frac{2+\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$;

$$x^2=\frac{2-\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$.
_________________
Manager  B
Joined: 18 Jul 2018
Posts: 52
Location: United Arab Emirates

Show Tags

Bunuel wrote:
aalakshaya wrote:
Bunuel in this question, I took x = (x^2) and hence calculated the roots for (x^2)^2-2(x^2)+1 by the formula root(B^2-4ac) which turned out to be 0 and hence, I marked choice B. Am I missing something?

$$(x^2)^2-2(x^2)+1 =0$$

$$x^2=\frac{2+\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$;

$$x^2=\frac{2-\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$.

Hi Bunuel,

I was wondering how did you find the roots as illustrated above??
Is this some kind of formula??

Would appreciate your help!
THANKS
Math Expert V
Joined: 02 Sep 2009
Posts: 58465

Show Tags

JIAA wrote:
Bunuel wrote:
aalakshaya wrote:
Bunuel in this question, I took x = (x^2) and hence calculated the roots for (x^2)^2-2(x^2)+1 by the formula root(B^2-4ac) which turned out to be 0 and hence, I marked choice B. Am I missing something?

$$(x^2)^2-2(x^2)+1 =0$$

$$x^2=\frac{2+\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$;

$$x^2=\frac{2-\sqrt{4-4}}{2}$$ --> $$x^2=1$$ --> $$x=1$$ or $$x = -1$$.

Hi Bunuel,

I was wondering how did you find the roots as illustrated above??
Is this some kind of formula??

Would appreciate your help!
THANKS

Solving and Factoring Quadratics:

Hope it helps.
_________________
VP  P
Joined: 14 Feb 2017
Posts: 1219
Location: Australia
Concentration: Technology, Strategy
Schools: LBS '22
GMAT 1: 560 Q41 V26 GMAT 2: 550 Q43 V23 GMAT 3: 650 Q47 V33 GMAT 4: 650 Q44 V36 WE: Management Consulting (Consulting)

Show Tags

Correct me if i'm wrong but this is simply the difference of squares?

X^4 -2x + 1 =0
(x^2-1)(x^2-1)=0
(x-1)(x+1)(x-1)(x+1) = 0
X= 1 or -1

Therefore there are 2 distinct roots.

I had dyslexia during the GMATClub test in which this question came up and I thought for some reason it was asking for that formula b^2-root 4ac... forget the name of it!
_________________
Goal: Q49, V41

+1 Kudos if I have helped you
Intern  B
Joined: 06 May 2019
Posts: 28
Location: India
Concentration: General Management, Marketing

Show Tags

The statement becomes

(X^2 -1)^2=0

X=+-1

Thus, we have two values Re: M03-18   [#permalink] 25 Jul 2019, 20:06

Go to page   Previous    1   2   [ 26 posts ]

Display posts from previous: Sort by

M03-18

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

Moderators: chetan2u, Bunuel

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