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Can a king and a knight ever checkmate a lone king?

chessendgamesimpossibility

In chess, one side has a king and a knight; the other has only a king.

  1. Can the side with the knight ever deliver checkmate, even if the lone king plays as badly as possible?
  2. What about king and bishop against king?
  3. What about king and two knights against king, and why is that case different?
Show a hint

Think about how many squares next to the lone king the knight and the attacking king can cover between them, and where the lone king's escape squares are.

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