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प्रश्न
Find the sum to n terms of the series 3 × 8 + 6 × 11 + 9 × 14 +…
उत्तर
The given series is 3 × 8 + 6 × 11 + 9 × 14 + …
an = (nth term of 3, 6, 9 …) × (nth term of 8, 11, 14, …)
= (3n) (3n + 5)
= 9n2 + 15n
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