[Home]History of Pells equation

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Revision 6 . . December 14, 2001 9:45 am by AxelBoldt [copyedit]
Revision 5 . . December 14, 2001 9:44 am by AxelBoldt [copyedit]
Revision 4 . . December 14, 2001 9:18 am by Lee Daniel Crocker
Revision 3 . . December 14, 2001 9:15 am by N8chz
Revision 2 . . December 14, 2001 9:12 am by Taw [natural number -> positive integer]
Revision 1 . . December 14, 2001 9:09 am by N8chz
  

Difference (from prior major revision) (author diff)

Changed: 3c3
As motivation, consider the square root of two. It is often approximated 1.414..., which some might incorrectly interpret as 1.41414141414..., or 140/99. Likewise, the reciprocal? of the [square root of two]? to three [decimal place]?s is 0.707, which is suggestive of 0.70707070..., or 70/99. If 70/99 approximates the reciprocal of the square root of two, it follows that 99/70 approximates the square root of two. As it turns out, the square root of two is between 140/99 and 99/70. The arithmetic mean of these two rationals is 19601/13860. That number squared is 384199201/192099600. It turns out that 2 times the denominator? 192099600 is 384199200, which differs from the numerator? by only one. p = 19601 and q = 13860 satisfies the [Diophantine equation]? 2q2+1=p2. Any fraction of natural numbers p and q that satisfy this equation will be a reasonably good approximation for the square root of two.
As motivation, consider the square root of two. It is often approximated 1.414..., which some might incorrectly interpret as 1.41414141414..., or 140/99. Likewise, the reciprocal? of the [square root of two]? to three [decimal place]?s is 0.707, which is suggestive of 0.70707070..., or 70/99. If 70/99 approximates the reciprocal of the square root of two, it follows that 99/70 approximates the square root of two. As it turns out, the square root of two is between 140/99 and 99/70. The arithmetic mean of these two rationals is 19601/13860. That number squared is 384199201/192099600. It turns out that 2 times the denominator? 192099600 is 384199200, which differs from the numerator? by only one. p = 19601 and q = 13860 satisfies the [Diophantine equation]? 2q2 + 1 = p2. Any fraction of natural numbers p and q that satisfy this equation will be a reasonably good approximation for the square root of two.

Changed: 6c6
:nq2+1=p2
:nq2 + 1 = p2

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