Here's another question from Advanced Engineering Mathematics by Greenberg [Ex 1.2 Q5]:
For what values of the constant $\lambda$ will $y = \exp(\lambda x)$ be a solution of the differential equation? If there are no such $\lambda$'s, state that $y^\prime + 3y = 0$
First of all, I couldn't understand the question because of the thing called $\exp$ in $y = \exp(\lambda x)$. May I know what is $\exp$? I'm confident that if I get to know what $\exp$ is then I can take it from there.