## Elliptic curves, inflection points and divisors [closed]

I'm studying basics of elliptic curves. I'm reading An Elementary Introduction to Elliptic Curves by Leonard Charlap and David Robbins. It is stated there that the divisor of a line (i.e. a polynomial of the form $ax + by + c$) can have only few forms, among them is $3\langle P \rangle - 3\langle \mathcal{O}\rangle$. I tried to find an example of a curve and a line on it that has such divisor, but to no avail. Can anyone provide an example? If it helps, they suggest that $P$ is an inflection point.

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This isn't the right level of question of this site, I'm afraid. You should try math.stackexchange.com. (see the FAQ here: mathoverflow.net/faq) – Alon Amit Sep 12 2011 at 7:29