Loïc Grenié on Thu, 19 Oct 2017 10:24:17 +0200

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Re: polinterpolate on reciprocals


On 2017-10-19 at 10:13 GMT+02:00 Kevin Acres wrote:
I noticed this effect today:

? polinterpolate([6,15,28,45,66,91])
2*x^2 + 3*x + 1
? polinterpolate([1/6,1/15,1/28,1/45,1/66,1/91])
-17/61776*x^5 + 6289/1081080*x^4 - 21139/432432*x^3 + 15997/77220*x^2 -
27509/60060*x + 1384/3003

In the second example I would have expected 1/(2*x^2 + 3*x + 1) rather
than the value given.

Am I doing something wrong here?

    Not really but you are expecting something wrong. 1/(2x^2+3x+1) is not
   a polynomial and polinterpolate always returns polynomials.