If sum of first n terms of an AP 2n2 + 5n. Then find S20

Afrose Asmaa's image
Afrose Asmaa
Oct. 29, 2017, 8:04 p.m.

Answers!

Davneet Singh's image
Davneet Singh
Oct. 30, 2017, 9:44 p.m.

Hello

We just put n = 20 in Sn

 

Given Sn = 2n2 + 5n

Putting n = 20

S20 = 2(20)2 + 5(20)

S20 = 2(400) + 100

S20 = 800 + 100

S20 = 900

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