Polynom subtraction is ok.
What is needed is derivation of sum of monom d/dx ( x^a) = a x^a-1 to do for financial marcket index study.
The aim is to derive g(x) = (f(x)-h(x+delta)) h(x) belonging to finacial market indexes.
One one derivation is donne d²/dx... can be done recursively.
Diff: