Delay differential equation Memes

The mathematical pun here is absolutely devastating. What we're looking at is a delay differential equation (DDE), where x(t-τ) indicates a time delay. In math terminology, these are called "retarded differential equations" because they contain a delayed (retarded) argument. Nothing quite captures the essence of being a mathematician like getting excited about an equation only to realize it's going to make your life significantly more difficult. Regular differential equations weren't painful enough, apparently. The face of pure mathematical despair in those bottom panels is what I see in the mirror during exam week.