Question

If the sum of n terms of an ap be 3n^2 +5n, then which of its term is 164?

Answer 1

Sn = 3n²+5n
S1 =a1 = 8
so 1st term is 8

now S2 -S1 = a2

so
a2 = 22-8
a2 = 14

now d = a2-a1
so d = 6

now An = a+(n-1)d
plug the values simply
164 = 8 + (n-1)6
156/6 = n-1
162/6 = n
=> n = 27

Answer 2

Answer:

27

Step-by-step explanation:

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