Hello, mathdonkey!

We want: .A large pizza franchise delivers large pizzas for $16. The equation: .

describes the profit, , based on the increase, , in the price of their large pizzas.

Determine the range of prices, to the nearest cent, for which the franchise

could sell each pizza and still make a profit of at least $640.

We want to know when: . .isabovethe x-axis.

Since the graph is a down-opening parabola, the curve is above the x-axis

. .its x-intercepts.between

For the x-intercepts, we have: .

Quadratic Formula: .

So we have: .

The franchise can raise the price per pizza by $2.48 or by $21.52

. . or anything in between, and still make at least $640.

The price can range from per pizza.