Last visit was: 25 Apr 2026, 09:34 It is currently 25 Apr 2026, 09:34
Home
Messages
Tests
Schools
Events
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
mikemcgarry
User avatar
Magoosh GMAT Instructor
Joined: 28 Dec 2011
Last visit: 06 Aug 2018
Posts: 4,474
Own Kudos:
30,884
 [11]
Given Kudos: 130
Expert
Expert reply
Posts: 4,474
Kudos: 30,884
 [11]
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 03 Mar 2017, 17:28
3
Kudos
Add Kudos
8
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

25% (medium)

Question Stats:

83% (02:21) correct 17% (02:10) wrong based on 304 sessions

History

Date
Time
Result
Not Attempted Yet
A sequence is defined by \(a_{n} = (a_{n-2})^2 - (a_{n-1})\) for all terms n > 2, and \(a_1 = 2\) and \(a_2 = 1\). What is the value of \(a_7\)?
(A) – 64
(B) – 7
(C) 38
(D) 88
(E) 128

This is the final problem from a set of challenging GMAT Quant practice question. For the whole collection, as well as the OE for this question, see:
Challenging GMAT Math Practice Questions

Mike :-)
ShowHide Answer
Official Answer
E
avatar
Funsho84
avatar
Joined: 08 Sep 2016
Last visit: 13 Aug 2022
Posts: 74
Own Kudos:
69
 [3]
Given Kudos: 25
Posts: 74
Kudos: 69
 [3]
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 03 Mar 2017, 17:58
3
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I think the Answer is E.

Did it the brute force way - about 3 minutes
avatar
Jayeshvekariya
avatar
Joined: 03 Jan 2017
Last visit: 27 Mar 2017
Posts: 23
Own Kudos:
18
 [1]
Given Kudos: 5
Posts: 23
Kudos: 18
 [1]
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 03 Mar 2017, 20:28
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Put the values in equation.
a1 =2
a2=1
a3=3
a4=-2
a5=11
a6=-7
a7=128. Ans. E

Hit kudos if you like...

Sent from my MotoG3 using GMAT Club Forum mobile app
User avatar
Nightmare007
User avatar
Joined: 26 Aug 2016
Last visit: 05 Aug 2020
Posts: 426
Own Kudos:
447
 [1]
Given Kudos: 204
Location: India
Concentration: Operations, International Business
Schools: ISB '20 (M) Simon '21 (WL)
GMAT 1: 690 Q50 V33
GMAT 2: 700 Q50 V33
GMAT 3: 730 Q51 V38
GPA: 4
WE:Information Technology (Consulting)
Products:
My Reviews
Schools: ISB '20 (M) Simon '21 (WL)
GMAT 3: 730 Q51 V38
Posts: 426
Kudos: 447
 [1]
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 16 Mar 2017, 22:50
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
a1 =2;a2=1;a3=3;a4=-2;a5=11;a6=-7;a7=128, keep values to get the series , Hit Kudos if you liked it.
User avatar
KrishnakumarKA1
User avatar
Joined: 05 Jan 2017
Last visit: 13 Oct 2020
Posts: 398
Own Kudos:
314
Given Kudos: 15
Location: India
Posts: 398
Kudos: 314
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 17 Mar 2017, 01:17
Kudos
Add Kudos
Bookmarks
Bookmark this Post
a1 =2
a2=1
a3=3
a4=-2
a5=11
a6=-7
a7=128.

Option E
User avatar
ManasviHP
User avatar
Joined: 12 Jan 2018
Last visit: 12 Jul 2020
Posts: 40
Own Kudos:
55
Given Kudos: 36
Location: India
Concentration: General Management, Marketing
Schools: Tepper '22 (S)
GMAT 1: 680 Q49 V32
WE:Engineering (Energy)
Schools: Tepper '22 (S)
GMAT 1: 680 Q49 V32
Posts: 40
Kudos: 55
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 07 Feb 2018, 02:54
Kudos
Add Kudos
Bookmarks
Bookmark this Post
a3= 4-1 = 3
a4= 1-3= -2
a5= 9 + 2= 11
a6= 4-11 = -7
a7= 121 + 7 = 128
Option E

Posted from my mobile device
User avatar
testcracker
User avatar
Joined: 24 Mar 2015
Last visit: 02 Dec 2024
Posts: 199
Own Kudos:
135
Given Kudos: 541
Status:love the club...
Posts: 199
Kudos: 135
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 19 Mar 2018, 20:12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
mikemcgarry
A sequence is defined by \(a_{n} = (a_{n-2})^2 - (a_{n-1})\) for all terms n > 2, and \(a_1 = 2\) and \(a_2 = 1\). What is the value of \(a_7\)?
(A) – 64
(B) – 7
(C) 38
(D) 88
(E) 128

This is the final problem from a set of challenging GMAT Quant practice question. For the whole collection, as well as the OE for this question, see:
Challenging GMAT Math Practice Questions

Mike :-)
Show more

a3 = (a1)^2 - (a2)
= 3

a4 = (a2)^2 - (a3)
= -2

a5 = (a3)^2 - (a4)
= 11

a6 = (a4)^2 - (a5)
= -7

a7 = (a5)^2 - (a6)

=128 = C the answer

thanks
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,986
Own Kudos:
1,117
Posts: 38,986
Kudos: 1,117
A sequence is defined by an = (an-2)^2 - (an-1) for all terms n = 2, a 19 Jun 2025, 04:10
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Bunuel
Math Expert
109827 posts
Krunaal
Tuck School Moderator
852 posts