Counterexample

Is this true?

All the classical equations satisfy a maximum principle

No — it is false.

The counterexample

The object that kills this claim comes with Trap Analysis.

86 counterexamples are free — including most of the ones Part C leans on hardest.

Keep practicing

Limit assumed to exist

Reasoning with a limit before establishing there is one. limsup is not lim.

See real exam options built on this mistake Drill statements like this

Go deeper· Explained in full in The three classical equations· Asked in CSIR NET December 2025· From Partial Differential Equations › Laplace, heat and wave equations: separation of variables

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