Question

How do I do this problem?

n an
1 1
2 6
3 11
4 16

When n equals 8, what does an equal?

Answer 1

You can tell it's an arithmetic sequence because \[
\large
a_{n+1} -a_n=5
\]

Answer 2

Arithmetic sequences have the form: \[
a_n = a_1 + (n-1)d
\]

Answer 3

In this case \(d = 5\) and \(a_1=1\), so our equation is \[
a_n = 1 + (n-1)5
\]

Answer 4

But that is not the question... your formula is:\[a_n = a_1 + (n - 1)d\]The \(d\) was stated by @wio: \(5\).

Answer 5

So you want to substitute \(n=8\) into the equation to find \(a_8\).

Answer 6

So, the formula is:\[a_n = 1 + 5(n - 1)\]Now substitute \(n = 8\).

Answer 7

So the answer would be 36, correct?

Answer 8

Yes

Answer 9

:D Thank you both, yall were A LOT of help!! <3