How do you determine whether the sequence #80, 40, 20, 10, 5,...# is arithmetic and if it is, what is the common difference?
To find if a sequence is arithmwtic, geometric or neither you have to check if either the difference (arithmetic sequence) or quotient (geometric sequence) between any 2 consecutive terms is constant.
The quotient of 2 consecutive terms is constant
No.. its not
And, their common ratio is
Therefore this sequence is geometric .
It would be arithmetic if the next term was formed by addition or subtraction.