Diophantine equations of the form x^3-dy^3=1

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Discussion Overview

The discussion revolves around Diophantine equations of the form x3 - dy3 = 1, specifically seeking integer solutions (x, y) for various integer values of d. Participants explore the nature of solutions based on whether d is a perfect cube or cube-free, and the implications of these classifications on the number of solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that for perfect cube values of d, the equation has finitely many solutions, but expresses uncertainty about other cases.
  • Another participant suggests that if d is a cube-free integer and the number of solutions is finite, then the modified equation x3 - d(n3)(y3) = 1 also has a finite number of solutions.
  • A different participant claims there are no solutions for x > 1 when d is a cubed integer, except for the special case of x = 0, d = 1, and y = -1, due to the nature of cubed integers being spaced apart.
  • This same participant also mentions that there are infinite solutions when y = 1, as x > 1 would satisfy d = x3 - 1.
  • Another participant references the Delaunay-Nagell theorem, indicating that it involves advanced algebraic techniques that may be challenging for those with limited mathematical background.

Areas of Agreement / Disagreement

Participants express differing views on the nature and number of solutions based on the characteristics of d, indicating that multiple competing views remain and the discussion is not resolved.

Contextual Notes

Some claims depend on specific definitions of cube-free integers and the nature of cubed integers, which may not be fully explored or agreed upon in the discussion.

Mathguy15
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I was recently thinking about these diophantine equations. I'm looking for solutions (x,y) in integers with d as an integer also. I have found that whenever d is a perfect cube, the equation has finitely many solutions. However, I can't seem to figure anything else out regarding equations of this type. Any ideas?MathguyEDIT:oh, and i don't know any advanced mathematics except for some linear algebra and bits and pieces of abstract algebra. So, please don't overwhelm this mere high schooler. Thanks
 
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Oh, and I've also figured out that if d is a cube-free integer such that the number of solutions to the equation is finite, then all integers of the equation x^3-d(n^3)(y^3)=1 also has a finite number of solutions.
 
Well, we know it has no solutions x>1 (There's a special case x=0, d=1, and y=-1, though) when d is a cubed integer, as then d^3*y^3 would also be a cubed integer. And since there is no difference between two cubed integers that is only 1 (they grow further and further apart from each other), there is a finite number of solutions.

And there is an infinite number of solutions when y=1, as then x>1 would be also have d=x^3-1 to make the solution true. But on the specifics of x=/=1 and y=/=1, I do not know.
 
Look up Delaunay-Nagell theorem (or equation). However, this result uses advanced algebraic techniques, so you might not be ready to understand the proof (yet!).
 

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