Question

Write a rule for the nth term of the sequence.

Use your rule to find a 100-
-11, 5, 21, 37, 53, ...

Answer 1

The rule for given sequence is: a_n = -27+16n

And the 100th term is: 1573

Explanation:

Given sequence is:

-11, 5, 21, 37, 53, ...

Here

`a_1 = -11\\a_2 = 5\\a_3 = 21\\a_4 = 37`

First of all, we have to find if this is an arithmetic sequence

For that purpose, the common difference has to be found. Common difference, denoted by d, is the difference between consecutive terms of an arithmetic sequence

So,

`d = a_2 -a_1 = 5-(-11) = 5+11 = 16\\d = a_3 -a_2 = 21-5 = 16\\d = a_4-a_3 = 37-21 = 16`

As the common difference is same, the sequence is an arithmetic sequence

General rule for arithmetic sequence is:

`a_n = a_1+(n-1)d`

Putting values

`a_n = -11+(n-1)(16)\\a_n = -11+16n-16\\a_n = -27+16n`

For 100th term,

Putting n=100

`a_(100) = -27+16(100)\\a_(100) = -27+1600 = 1573`

Hence,

The rule for given sequence is: a_n = -27+16n

And the 100th term is: 1573