Black–Scholes equation - Wikipedia
https://en.wikipedia.org/wiki/Black–Scholes_equationThe following derivation is given in Hull's Options, Futures, and Other Derivatives. That, in turn, is based on the classic argument in the original Black–Scholes paper. Per the model assumptions above, the price of the underlying asset (typically a stock) follows a geometric Brownian motion. That is where W is a stochastic variable (Brownian motion). Note that W, and consequently its infinitesi…