A company that produces portable cassette players estimates that the profit P (in dollars) for selling a particular model is P=-76x^3+4830x^2-320000, 0 is less than or equal to x is less than or equal to 50, where x is the ad expense (in tens of thousands of dollars). using this model, find the smaller of two ad amounts that will yield profit of $800000.

Answer 1

you must have a method of solving
800000 = -76x^3 + 4830x^2 - 320000

Wolfram yields two answers,
one of appr 18 , the other appr 59.3

http://www.wolframalpha.com/input/?i=solve+800000+%3D+-76x%5E3+%2B+4830x%5E2+-+320000