Step 1
Given:
The sequence,
\(80, 40, 20, 10, 5,...\)
Step 2
To check it is arithmetic sequence, calculate the common difference
\(d = a_2 - a_1\)

\(= 40 - 80\)

\(= -40\)

\(d = a_3 - a_2\)

\(= 20 - 40\)

\(= -20\) Since, the common difference d is not same. The given sequence is not arithmetic.

\(= 40 - 80\)

\(= -40\)

\(d = a_3 - a_2\)

\(= 20 - 40\)

\(= -20\) Since, the common difference d is not same. The given sequence is not arithmetic.