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📐 Mathematics  ·  Sequences and Series  ·  JEE

In an AP, if Sn = 3n² + 5n, find the nth term.

Answer: 6n + 2.

  • A 6n + 2
  • B 6n - 2
  • C 6n + 5
  • D 3n + 5

Correct answer: A. 6n + 2

Explanation: Tn = Sn - S(n-1) = 3n²+5n - 3(n-1)²-5(n-1) = 6n - 3 + 5 = 6n + 2.

Each bar grows by the common difference d=3a1=2a2=5a3=8a4=11d=3

Bar heights for AP 2, 5, 8, 11 with the common difference d=3 marked between consecutive terms.

Concept context

Arithmetic progressions, geometric progressions, and sums

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