A cell phone company’s profit is modeled by the function p(x) = 10x − x2 − 1, where p is expressed in thousands of dollars and x is the number of phones sold in hundreds. How many phones must the company sell to make a profit of more than $15,000?

Answer 1

P(x) = 10x - x^2 - 1 = 15.
-x^2 + 10x - 1 - 15 = 0.
-x^2 + 10x - 16 = 0.
Solve using Quadratic Formula and get:
X = 2 = 200 Phones.
X = 8 = 800 Phnes.

Answer 2

The profit, P(x), of a software company, in thousands of dollars, is given by the equation P(x) = "-10x+" 110x + 10000, where x is the amount spent on advertising, in thousands of dollars. Determine the least amount spent on advertising that will result in a profit of at least $8 000 000.