Math, asked by audreyfrary6521, 1 year ago

The sum of n terms of an ap is 5n^2/2 + 3n/2 find the nth term and 20th term

Answers

Answered by pawan4585
2
Sn = (5n2 + 3n) / 2

Therefore, S20 = [5 (20)2 + 3 (20) ] / 2

Thus S20 = 2060 / 2 = 1030

 

S19 = [5 (19)2 + 3 (19)] / 2  = 1862 / 2

Thus, S19 = 931

 

Tn =  Sn - Sn-1

Therefore, T20 = S20 - S19

T20 =  1030 - 931 = 99

 

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