What is the greatest prime factor of 4^17 - 2^27?
I can't figure this one out.
Thanks
GMAT Forum
3 postsPage 1 of 1
- rjdog21
- Posts: 4
- Joined: Mon Mar 02, 2009 8:58 am
- balaji.raghavan.t
- Students
- Posts: 2
- Joined: Mon Oct 27, 2008 10:03 pm
Re: Prime factors
Hi!
4^17 - 2^27
= (2^2)^17 - 2^27
= 2^34 - 2^27
= 2^27 [2^7 - 1] -->Take the smallest power of 2 common out of the expression
= 2^27 [127]
So the greatest prime factor is 127.
Hope this helps!
4^17 - 2^27
= (2^2)^17 - 2^27
= 2^34 - 2^27
= 2^27 [2^7 - 1] -->Take the smallest power of 2 common out of the expression
= 2^27 [127]
So the greatest prime factor is 127.
Hope this helps!
- RonPurewal
- Students
- Posts: 19744
- Joined: Tue Aug 14, 2007 8:23 am
Re: Prime factors
hi -
the above poster's solution is correct, but i think you've copied the problem incorrectly.
unless there are two almost identical problems floating around out there (a situation that is almost certainly not the case), this is supposed to be 4^17 - 2^28.
check out this link:
post21747.html
there are 5 other threads already dealing with this problem, as shown at the bottom of the linked thread.
the above poster's solution is correct, but i think you've copied the problem incorrectly.
unless there are two almost identical problems floating around out there (a situation that is almost certainly not the case), this is supposed to be 4^17 - 2^28.
check out this link:
post21747.html
there are 5 other threads already dealing with this problem, as shown at the bottom of the linked thread.
3 posts Page 1 of 1