Answer
$-x+61$
Work Step by Step
The nth term of an arithmetic sequence can be found as: $a_n=a_1+(n-1)d$.
where, $a_1$ is the first term and $d$ is the common difference(is the difference between a term and the term proceeding it), that is, $d=a_n-a_{n-1}$
From the given series, we have:
$a_1=6x-9$
$d=a_2-a_1=5x+1-(6x-9)=-x+10$.
Substitute these values in the formula above and evaluate for $n=8$( eighth term).
$a_8=6x-9+(8-1)(-x+10) \\
a_8=6x-9+7(-x+10)\\
a_8=6x-9-7x+70\\
a_8=-x+61$
Therefore, the eighth term of an arithmetic sequence is: $-x+61$
