Question

the sum of n term of an AP is 3n square + 5n. find the AP and its 15th term.

Answer 1

hello Frnd

Given

Sn = 3n^2 + 5n

To find AP we will

put n = 1

S1 = 3 (1)^2 + 5(1)

= 8
It is the first term of AP

Also

n = 2

S2 = 3(2)^2 + 5(2)
= 22

First term is 8

there fore 2nd term
= 22 - 8 = 14

Hence
a = 8

d = 14 - 8 = 6

hence the required AP
8, 14, 20, 26.....

Now 15th term

a15 = a + ( n -1)d

a15 = 8 + 14 (6)

= 92



hope it helps
#jerri

Answer 2

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