How do I do this problem?

n an
1 1
2 6
3 11
4 16

When n equals 8, what does an equal?

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?

anonymous · Answer

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

anonymous · Answer

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

anonymous · Answer

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

parthkohli · Answer

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

anonymous · Answer

So you want to substitute $n=8$ into the equation to find $a_8$.

parthkohli · Answer

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

anonymous · Answer

So the answer would be 36, correct?

anonymous · Answer

Yes

anonymous · Answer

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