MathDB
Putnam 1988 A2

Source:

August 6, 2019
Putnam

Problem Statement

A not uncommon calculus mistake is to believe that the product rule for derivatives says that (fg)=fg(fg)' = f'g'. If f(x)=ex2f(x)=e^{x^2}, determine, with proof, whether there exists an open interval (a,b)(a,b) and a nonzero function gg defined on (a,b)(a,b) such that this wrong product rule is true for xx in (a,b)(a,b).