1. The problem statement, all variables and given/known data y=9-x 2. Relevant equations 3. The attempt at a solution dy/dx=-9-xln9 We are provided with the answers. I do not understand the concept behind how to get from the question to the solution. What rule(s) are applied? If somebody could solve this single question, or a similar one, in a step-by-step method, I would greatly appreciate it.