multiplying polynomials

Question

The cost of a video game can be modeled by the equation C = 5x -2. The number of games sold can be modeled by the equation N = 8x + 5. Write a model for the revenue from the sale of the games.

Answer 1

If “Cost” means the price per unit, then the revenue (total $ the company will bring in from sales) is just C⋅N.

(For example, if they sell 100 games at $5 per game, they bring in $500.)

So, C(x) = (5x - 2)(8x + 5)

FOILing that out gives C(x) = 40x² + 9x - 10