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Quarting the cube (Posted on 2013-02-28) Difficulty: 3 of 5

Select integer x and triangular number y such that 8y=3x^4-2x^2-1.

Prove that y is divisible by 28 - or find a counter-example.

See The Solution Submitted by broll    
Rating: 5.0000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts re: computer exploration shows likely true -- no proof | Comment 4 of 6 |
(In reply to computer exploration shows likely true -- no proof by Charlie)

Cn,

1. You somehow missed x=1 y=0; a valid triangular number
2. You were very close to proof, not verification- all you needed
was to assume a  linear recurrence equation and to show that it assures divisibility by 28.
3.Please read my post and ,if needed, comment on it.


  Posted by Ady TZIDON on 2013-03-01 21:24:39
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