GMAT Changed on April 16th - Read about the latest changes here

It is currently 21 Apr 2018, 19:33

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If f(x)=√(x^2−2x+1), what is f(9)?

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 44599
If f(x)=√(x^2−2x+1), what is f(9)? [#permalink]

Show Tags

New post 15 Apr 2018, 10:00
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (00:31) correct 0% (00:00) wrong based on 48 sessions

HideShow timer Statistics

Expert Post
examPAL Representative
User avatar
B
Joined: 07 Dec 2017
Posts: 292
If f(x)=√(x^2−2x+1), what is f(9)? [#permalink]

Show Tags

New post 15 Apr 2018, 10:30
Bunuel wrote:
If \(f(x)=\sqrt{x^2−2x+1}\), what is f(9)?

A. -8
B. 5
C. 8
D. 9
E. 82


We'll show two approaches.

The Precise approach involves straight up calculation:
9^2 - 2*9 + 1 = 81 - 18 + 1 = 64, the square root of which is 8.
Note that the 'square root function' always returns a positive number which is why (A) is incorrect.
(C) is our answer.

We could also have estimated the answer, an Alternative approach.
We know that the square root of x^2 is x. Since we're asked for the square root of something smaller than x^2 (e.g. x^2 - 2*x+1) we know the answer must be smaller than x.
Only C and B make sense but we can estimate (without calculating) that (B) is too far: 5^2 = 25 and 81 - 18 + 1 is about 60, much larger than that.
Note that in this case estimation is not necessary as the equation is simple, however it can be very useful for difficult calculations.
_________________

David
Senior tutor at examPAL
Signup for a free GMAT course
Image
Image
We won some awards:
Image
Join our next webinar (free)
Save up to $250 on examPAL packages (special for GMAT Club members)

1 KUDOS received
Intern
Intern
avatar
Joined: 15 Apr 2018
Posts: 2
Re: If f(x)=√(x^2−2x+1), what is f(9)? [#permalink]

Show Tags

New post 15 Apr 2018, 21:51
1
This post received
KUDOS
f(x) = sqrt{(x-1)^2} = x - 1
f(9) = 9 - 1 = 8
Answer = C


Sent from my iPad using GMAT Club Forum
Intern
Intern
avatar
B
Joined: 04 Apr 2018
Posts: 3
Re: If f(x)=√(x^2−2x+1), what is f(9)? [#permalink]

Show Tags

New post 18 Apr 2018, 10:26
anwer is C car a square root can never be negative
Re: If f(x)=√(x^2−2x+1), what is f(9)?   [#permalink] 18 Apr 2018, 10:26
Display posts from previous: Sort by

If f(x)=√(x^2−2x+1), what is f(9)?

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.