Question

A company produces portable cassette players estimates that the profit P (in dollars) for selling a particular model is P=-76x^3+4830x^2-320,000, 0 ≤ x ≤ 50, where x is the advertising expense (in tens of thousands of dollars). Using this model, find the smaller of two advertising amounts that will yield a profit of $800,000.

Answer 1

This is just algebra I. You want x where

-76x^3+4830x^2-320000 = 800000

I suggest a graphing utility, as this has no rational roots.