How can Taylor expansion show that the one-sided formula is O(h^2)?

[hunter55]

Homework Statement

Using Taylor expansion, show that the one-sided formula (f_-2-4f_-1+3f)/2h is indeed O(h2). Here f-2, for example, stands for f(xo-2h), and f-1 = f(xo-h), so on.

The Attempt at a Solution

Can some1 help me get starte, I am greatly confused

 

[Dick]

Taylors expansion let's you relate f(x+h) to powers of h and derivatives of f, right? Use it. If you have something like f(x-3h) just substitute -3h for h in the taylor expansion of f(x+h). I don't think that expression of (Oh^2). Are you sure you copied it correctly?