Algebra-1

Question Analysis
This question assesses the student's understanding of the explicit formula for an arithmetic sequence, particularly when the common difference is negative. The given values are the first term () and the common difference (), and the task is to find the 9th term.

Key Concept Explanation
The explicit formula for an arithmetic sequence is . When the common difference is negative, the sequence decreases.

Step-by-step Solution
1. Identify the given values: ,