Question

Find an equation for the nth term of the arithmetic sequence. 9, 11, 13, 15

Answer 1

An arithmetic sequence has the form as

`a_n=a_1+(n-1)d`
where
`a_n` = n-th term,

`a_1` = first term,
d = common difference

We can see that 11 – 9 = 13 – 11 = 15 – 13 = 2. So the common difference is d = 2.
The first term is
`a_1=9`. So the n-th term of the sequence is

`a_n=9+(n-1)(2)=9+2n-2=7+2n`
So the answer is
`a_n=7+2n`