Answer:
a68 = -85.2
Explanation:
The formula for an arithmetic sequence is
an = a1+d(n-1)
a1 =8.6 (it is the first term)
We can find the common difference by taking the second term and subtracting the first term
7.2-8.6 =-1.4
d=-1.4
n = the term number we are looking for
an = 8.6 -1.4(n-1)
We are looking for the 68th term so n=68
a68 = 8.6 -1.4(68-1)
= 8.6 -.1.4(67)
= 8.6-93.8
=-85.2