BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Factor Problem

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 324
Joined: Mon Jul 05, 2010 6:44 amFollowed by: 3 members
Location: London
Thanked: 70 times

by kmittal82 » Fri Jul 09, 2010 7:57 am
4^17 = 2^34

4^17 - 2^28 = 2^34 - 2^28 = 2^28(2^6 - 1)

Now, 2^6 - 1 = 63, and the greatest prime factor for that is 7 (63 = 3x3x7)

Hence, answer should be (D)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 294
Joined: Wed May 05, 2010 4:01 am
Location: india
Thanked: 57 times

by amising6 » Fri Jul 09, 2010 7:59 am
monteleone82 wrote:Please help with the question below!


What is the greatest prime factor of 4^17 - 2^28?

A. 2
B. 3
C. 5
D. 7
E. 11
4^17 - 2^28
(2^2)^17 - 2^28
2^34-2^28
2^28(2^6-1)
2^28(64-1)
2^28(63)
2^28*3*3*7
so gretaest prime factor=7
Ideation without execution is delusion
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 10
Joined: Thu Sep 03, 2009 11:38 am

by monteleone82 » Fri Jul 09, 2010 8:10 am
How do you get (2^6-1)? I am confused with that part
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 324
Joined: Mon Jul 05, 2010 6:44 amFollowed by: 3 members
Location: London
Thanked: 70 times

by kmittal82 » Fri Jul 09, 2010 8:11 am
monteleone82 wrote:How do you get (2^6-1)? I am confused with that part
2^34 - 2^28

Taking 2^28 as common:

2^28(2^6 - 1)

2^28 x 2^6 = 2^34 [a^b x a^ c = a^(b+c) ]
2^28 x 1 = 2^28

Any clearer ?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 10
Joined: Thu Sep 03, 2009 11:38 am

by monteleone82 » Fri Jul 09, 2010 8:15 am
Got it. thanks.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1