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Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Source: — Quantitative Reasoning |
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by mohitsharda » Wed Nov 21, 2012 7:12 am
4^17 = (2^2)^17
=> 2^(2*17) = 2^34

Now, for the question

4^17 - 2^28 = 2^34 - 2^28
=> Take 2 ^28 common out
=> (2^28)*((2^6)-1)
=> (2^28)*(64-1) = (2^28)*63
=> (2^28)*7*(3^2)

So. the greatest prime factor is 7.
MS
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