Question

Determine whether the sequence converges or diverges. If it converges, give the limit.

Answer 1

Answer:

The given series converges and $\lim_{n \to \infty} a_n =0$

Step-by-step explanation:

Given is 108, -18, 3,...

It is an alternate series. An alternate series is convergent if:

1. The series is decreasing.

2. If the last term (n-th term) of series converges to 0.

Since each next term is less than its preceding term, so it is decreasing.

First term, a = 108

Second term = -18

Common ratio, r = -18/108 = -1/6

General term, aₙ = a*rⁿ = 108*(-1/6)ⁿ

When n increases to infinity, the exponent term will decreases to zero, and last term (n-th term) will converge to 0 as well.

Hence, the given series converges.

Now limit will be: $\lim_{n \to \infty} a_n$

$\lim_{n \to \infty} 108*(-1/6)^n \\= 108*(-1/6)^\infty \\= 108*(1/\infty) \\= 108*0 \\= 0$

Hence, $\lim_{n \to \infty} a_n =0$