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Prime factor of big numbers?

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by VP_RedSoxFan » Thu Jul 31, 2008 9:20 am
I think this one has been answered before, but I'll help out anyway:

The first thing I'd do is turn the 2^28 into 4^14, giving you 4^17 - 4^14.

Then, I'd factor our the 4^14 leaving me with

4^14(4^3 - 1)

I know the prime factors represented by 4^14 will just be 28 2's. So as long as I get something more than a 2 as a prime factor of 4^3 -1 then that will be the answer. 4^3 - 1 = 63 whose prime factors are 3, 3, 7. So the prime factorization of this difference is 28 2's, 3, 3, and 7, the largest, of course, is 7.
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by Gouman » Tue Jun 23, 2009 12:08 am
Nice response. I like that.
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by BlindVision » Tue Jun 23, 2009 12:39 am
Understandable response! Good job!
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