Question

1. Find the general rule for each arithmetic or geometric sequence.
2. Calculate the 10th term for each sequence.
a) a=a sub n-1*n
a sub one=9
b) a sub n=a sub n-1 + 8
a sub 1=-17
c) a sub n=a sub n-1 + 2
a sub 1=9
d) a=n*a sub n-1
a sub one=1


I don't understand how to determine if it is an arithmetic sequence or a geometric sequence if there is no sequence and I don't understand how to find the general rule.

Answer 1

clearly you have skipped the definitions.

arithmetic has terms which differ by the same amount

geometric has terms with a common ratio, one to the next.

a) has a ratio which changes: A(n) = A(n-1)*n
A(n)/A(n-1) = n, which is not constant
not GP or AP

b)That +8 is a dead giveaway. Each term is 8 more than the last, so it's an AP

c) same idea, AP

d) exactly the same as (a)