Re: true or false: (x^5 - x) has inflexion point at origin, (x^4 - x) doesn't

In article <1124960183.220303.114120@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
<john_ramsden@xxxxxxxxxxxxxx> wrote:

>I've always presumed that an inflection of y = y(x) is a
>point where y'' = 0, whether this is an extrema of y' or
>only a turning point (which is apparently the distinction
>some definitions are intended to make).

>But obviously opinion is still divided, which for a concept
>so basic and long-established is astonishing.

I'm not aware of any published source that agrees with your
definition. To come back to the Subject line, nobody would
say that x^4 - x has an inflection at x=0.

Robert Israel israel@xxxxxxxxxxx
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada
.

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