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Re: 2^16-1 [#permalink]
Expert Reply
Tricky one. You can solve it unfolding the expression using the (a-b)(a+b property or recognize a pattern

of 2^{16}-1 notice that the smallest root of two is 2^2 (essentially we do have multiple twos)

So at the core we do have \((2^2-1) = (2-1)(2+1)\) that is \(1*(2+1)\)

In the end we do have for QA \((2+1)(2^2+1)(2^4+1)(2^8+1)\)

Which is = to QB

C is the answer
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Re: 2^16-1 [#permalink]
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Very tricky and good question Thanks!!!Carcass
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Re: 2^16-1 [#permalink]
Is there anyone who can break this question down? I really can't wrap my head around it.
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Re: 2^16-1 [#permalink]
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Expert Reply
If you use

\(a^2-b^2=(a-b)(a+b)\)

Therefore

\((2^8-1^8)(2^8+1^8)\)

\((2^4-1^4)(2^4+1^4)(2^8+1^8)\)

\((2^2-1^2)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

\((2-1)(2+1)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

\((2+1)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

C is the answer
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Re: 2^16-1 [#permalink]
Carcass wrote:
If you use

\(a^2-b^2=(a-b)(a+b)\)

Therefore

\((2^8-1^8)(2^8+1^8)\)

\((2^4-1^4)(2^4+1^4)(2^8+1^8)\)

\((2^2-1^2)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

\((2-1)(2+1)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

\((2+1)(2^2+1^2)(2^4+1^4)(2^8+1^8)\)

C is the answer


Thank you. This was very helpful
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Re: 2^16-1 [#permalink]
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