Question

The sum of first n terms of an ap is 3n square + 6 and find the 10th term of the 15th term of the ap

Answer 1

given:

Sn = 3n^2 + 6

let n= 1

S1 = 3×1×1 + 6 = 9. (a1)

let n = 2

S2 = 3×2×2 + 6 = 18. (a1 + a2)

therefore.. a1 + a2 = 18

9 + a2 = 18

a2 = 18 - 9 = 9

common difference (d) = a2 - a1 = 0

for 10th term

a10 = a1 + (n-1)d

a10 = 9 + (10-1)×0

a10 = 9. ans

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