21-260: Pay No Attention to the Hint for Problem 2.1.23b

The WileyPLUS "Hint" for this problem is incorrect. The "transition from one type of behavior to another" is this: for some initial conditions, the solutions increase without bound as t approaches infinity; for other initial conditions, the solutions decrease without bound. You want to find the initial condition y(0)=a_0 that identifies the solution that separates these two types of behavior. The solution doesn't involve finding derivatives and setting them equal to zero.