Which term of the AP `-2,-7,-12, …` will be `-77` ? Find the sum of this AP upto the term `-77`.

Explanation

To solve the problem step by step, we will first determine which term of the arithmetic progression (AP) is -77 and then calculate the sum of the AP up to that term.

### Step 1: Identify the first term and common difference
The given AP is:
\[ -2, -7, -12, \ldots \]
- The first term \( A = -2 \).
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