Question

In an A.P if sum of its first n terms is 3n^2 + 5n and its kth term is 164, find the value of k.

Answer 1

Answer:

k=27

Step-by-step explanation:

sum of n terms = 3n²+5n

Let us calculate value of n= 1 and 2

S1= 3x1²+5x1

= 8

Sum of two terms , S2= 3x2²+5x2

S2=22

here first term= 8

second term= 22-8=14

Difference, d= 14-8= 6

Let a=8 is first term of AP and D=6 difference

Then, Kth term

= a+(k-1)d= 8+6x(k-1)

Given that kth term= 164

8+6(k-1)= 164

k-1=156/6

k-1=26

k=27

Therefore 164 is the 27th term of AP with 8 as first term and 6 as difference

Answer 2

Answer:answer is in attachment .

Step-by-step explanation: