I think that
Using the formula [f(a+h)-f(a-h)]/2h = f prime of a, prove that
[f(a+h) - 2f(a) + f(a-h)]/h^2 = f double prime of a.
I get [f(a+h) - 2f(a) + f(a-h)]/2h^2
Could someone show me the proof of this? It's driving me crazy.
My work
[[2f(a+h) - 2f(a)] - [f(a+h) - f(a-h)]]/2h/h = the above (I assume incorrect) answer