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Lucas squares (Posted on 2013-12-15) Difficulty: 3 of 5

Let n be an integer, and let (Ln) signify the nth Lucas Number.

((Ln)2+(Ln+1)2)2 - 5((L2n+2)*(L2n)-1) = 0

Prove it!

See The Solution Submitted by broll    
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re(3): Long solution. | Comment 4 of 6 |
(In reply to re(2): Long solution. by Jer)

I was thinking in terms of writing up the solution.

Your line 5 as given is in terms a statement limited to Lucas identities.

In fact, at that point, they no longer need to be Lucas identities; any integers we choose that satisfy the equality a^2-3ab+b^2 = -5 (and no others) are necessarily of the form {(L2n+2), (L2n)}  (or vice versa) simply because those numbers, and no others, satisfy the equality.

But if so, we no longer need to specify that they are Lucas identities as such. So I would say that the proof was complete at line 5.

That is the point I was trying to get at.




  Posted by broll on 2013-12-17 03:15:58
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