The sum of first n terms of an AP is (3n2 + 6n). The common difference of the AP is

Foundation

Mathematics Foundation

Sum of n terms of an AP

Question

The sum of first n terms of an AP is (3n² + 6n). The common difference of the AP is

– 3

College PredictorLive

Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.

Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA

Given S_n = (3n² + 6n).

$∴$ T₁ = S₁ = (3 × 1² + 6 × 1) = 9, S₂ = (3 × 2² + 6 × 2) = 24.

$∴$ T₂ = (S₂ – S₁) = (24 – 9) = 15.

Hence, d = (T₂ – T₁) = 15 – 9 = 6.