A sequence starts at 9, counted as its first term, and each term after that is 4 less than the one before it. What is its fifth term?

الشرح

Counting the start as the opening term, four further steps of four downwards reach five, then one, then three below zero, then seven below zero. Stopping after three steps names the term one place earlier, which is the usual way to fall short when the starting value is counted as a step of its own.