First, let's find which term is -81. The AP is 21, 18, 15... so the common difference 'd' is -3. Using the formula aₙ = a + (n-1)d: -81 = 21 + (n-1)(-3). Solving this gives n = 35, so the 35th term is -81.
Now, for 0 being a term: 0 = 21 + (n-1)(-3) gives n = 8. So yes, the 8th term is 0.
But yaar, in my own life's "arithmetic progression" of bills and repairs, something being zero is never a good term 😅. Like when my gym salary hits the account and immediately goes to fees, it feels like a zero-term – it exists on paper, but you never really get to hold it.
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