Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

 It is currently 21 Jul 2019, 06:36

### 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

# The function f is defined for all real numbers x as f(x)=x2−1. What is

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 56307
The function f is defined for all real numbers x as f(x)=x2−1. What is  [#permalink]

### Show Tags

09 Apr 2018, 02:01
00:00

Difficulty:

5% (low)

Question Stats:

97% (00:34) correct 3% (00:56) wrong based on 88 sessions

### HideShow timer Statistics

The function f is defined for all real numbers x as f(x) = x^2 − 1. What is f(f(3))?

A. 26
B. 47
C. 63
D. 75
E. 80

_________________
Senior Manager
Joined: 14 Feb 2018
Posts: 389
Re: The function f is defined for all real numbers x as f(x)=x2−1. What is  [#permalink]

### Show Tags

09 Apr 2018, 02:52
1
f(3) = 3^2 - 1 = 8

f(f(3) = f(8) = 8^2 - 1 = 63

Option C.

Sent from my Lenovo K53a48 using GMAT Club Forum mobile app
Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3359
Location: India
GPA: 3.12
Re: The function f is defined for all real numbers x as f(x)=x2−1. What is  [#permalink]

### Show Tags

09 Apr 2018, 04:48
Bunuel wrote:
The function f is defined for all real numbers x as f(x) = x^2 − 1. What is f(f(3))?

A. 26
B. 47
C. 63
D. 75
E. 80

Given: f(x) = $$x^2 - 1$$

f(f(x)) = f($$x^2 - 1$$) = $$(x^2 - 1)^2 - 1 = x^4 - 2x^2 + 1 - 1 = x^4 - 2x^2$$

Therefore, $$f(f(3)) = 3^4 - 2*3^2 = 81 - 18$$ = 63(Option C)
_________________
You've got what it takes, but it will take everything you've got
Intern
Joined: 16 Mar 2018
Posts: 46
Location: United Kingdom
GMAT 1: 650 Q45 V35
Re: The function f is defined for all real numbers x as f(x)=x2−1. What is  [#permalink]

### Show Tags

09 Apr 2018, 06:10
We can break x^2-1 =[x+1][x-1]
So f(3)= 4x2=8

And F(f(3))=f(8) = (8+1) (8-1) = 63

Option C :63

Sent from my iPhone using GMAT Club Forum
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 6967
Location: United States (CA)
Re: The function f is defined for all real numbers x as f(x)=x2−1. What is  [#permalink]

### Show Tags

10 Apr 2018, 17:09
Bunuel wrote:
The function f is defined for all real numbers x as f(x) = x^2 − 1. What is f(f(3))?

A. 26
B. 47
C. 63
D. 75
E. 80

f(3) = 3^2 - 1 = 8

f(f(3)) = f(8) = 8^2 - 1 = 63

So f(f(3)) = 63.

_________________

# Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Re: The function f is defined for all real numbers x as f(x)=x2−1. What is   [#permalink] 10 Apr 2018, 17:09
Display posts from previous: Sort by