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

 It is currently 19 Oct 2019, 00:53

### 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

# A function f has the property that f(3x-1)=x^2+x+1 for all real number

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58454
A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

26 Mar 2019, 23:14
00:00

Difficulty:

25% (medium)

Question Stats:

63% (00:40) correct 38% (01:17) wrong based on 56 sessions

### HideShow timer Statistics

A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

_________________
Intern
Joined: 27 Sep 2018
Posts: 37
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

26 Mar 2019, 23:40
We can write f(5) as f(3*2-1)
Now comparing with f(3x−1)=x^2+x+1
We get x=2
Putting in given equation we have 2^2+2+1=7

Posted from my mobile device
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 5020
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

27 Mar 2019, 01:24
Bunuel wrote:
A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

f(3x-1)= f(5)
at x= 2
so x^2+x+1 = 7 at x=2
IMOA
Manager
Joined: 04 Oct 2018
Posts: 159
Location: Viet Nam
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

27 Mar 2019, 03:45
Bunuel wrote:
A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

f(5) = f(3*2 - 1) = 2^2 + 2 + 1 = 7. Thus A
_________________
"It Always Seems Impossible Until It Is Done"
Senior Manager
Joined: 12 Sep 2017
Posts: 302
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

28 Mar 2019, 19:07
Archit3110 wrote:
Bunuel wrote:
A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

f(3x-1)= f(5)
at x= 2
so x^2+x+1 = 7 at x=2
IMOA

Hello Archit3110!!!

It took me some time to realize that I could equal both functions. ¿In which cases can we do this?

Kind regards!
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 5020
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

29 Mar 2019, 01:17
jfranciscocuencag wrote:
Archit3110 wrote:
Bunuel wrote:
A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

f(3x-1)= f(5)
at x= 2
so x^2+x+1 = 7 at x=2
IMOA

Hello Archit3110!!!

It took me some time to realize that I could equal both functions. ¿In which cases can we do this?

Kind regards!

jfranciscocuencag
well the only way to solve this question was to simplify the f(3x-1) ; such that it becomes equal to f(5). so x=2 was substituted
it all depends on the question and the function formula and whats been asked..
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8109
Location: United States (CA)
Re: A function f has the property that f(3x-1)=x^2+x+1 for all real number  [#permalink]

### Show Tags

29 Mar 2019, 08:37
Bunuel wrote:
A function f has the property that $$f(3x-1)=x^2+x+1$$ for all real numbers x. What is f(5)?

(A) 7
(B) 13
(C) 31
(D) 111
(E) 211

Since we want f(5), we should look for the value of x such that 3x - 1 = 5:

3x - 1 = 5

3x = 6

x = 2, so we have:

f(5) = f(3*2 - 1) = 2^2 + 2 + 1 = 7

_________________

# 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: A function f has the property that f(3x-1)=x^2+x+1 for all real number   [#permalink] 29 Mar 2019, 08:37
Display posts from previous: Sort by