I need help with this problem. this is what I got so far:

Question

P(x)=12x-(x^2/500)-680-4x-0.01x^2

P'(x)=12-0.004x-4-0.02x

P'(x)= -0.024x-8

x=8/0.024

My book says x=8/0.024 which somehow become 1000/3. They are the same when solved but how did they come up with 1000/3?

Answer 1

multiply numerator and denominator by 1000/8