Sum the series `3. 8+6. 11+9. 14+ . . . ` to `n` terms.

Explanation

To sum the series \(3 \cdot 8 + 6 \cdot 11 + 9 \cdot 14 + \ldots\) up to \(n\) terms, we first need to identify the general term of the series.

### Step 1: Identify the nth term of the series

The terms of the series can be expressed as:
- The first term: \(3 \cdot 8\)
- The second term: \(6 \cdot 11\)
- The third term: \(9 \cdot 14\)
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