I am sorry to tell you that the derivative is +6C/x^(7). I just looked it up. You can re-write the equation as -1C*x^(-6),so -6*-1= +6, and x^(-6) becomes x^(-7), so the derivative is +6C*x^(-7) or +6C/x^(7). Here's the website I found this at. It's really great if you have math questions...