perplexus.info :: Just Math : Quarting the cube

Quarting the cube (Posted on 2013-02-28)

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.)

re: computer exploration shows likely true -- no proof

| Comment 4 of 6 |

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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