An appliance store manager estimates that for x television ads run per day, R(x)=-0.01x^3+x^2-3x+200 refrigerators will be sold per month. Find R'(4) and interpret what it tells us about sales.
My answer was for every 4 TV adds, 1.16 refrigerators will be sold. Is this correct?

Question

anonymous · Answer

$$R'(x)=-0.03x^2+2x-3$$ plug 4 into it, we got 4.52. 
the first derivitive is the slope of the curve, so it should be the change amount of y when x change. I am wondering here should be when adds=4, adding more adds can increaset the refig sold by 4.52

anonymous · Answer

You are corrrect. I multiplied -.01 * 3 incorrectly

Thanks!!