Question 967155
A food truck sells 500 sandwiches per day when they charge $9 per sandwich. It sells 100 more sandwiches per day for each $1 decrease in price. What price should the vendor charge to maximize the profit? What would be the maximum profit?

My Work:

let x = number of money decrease
let y = profit

y=500+9x
y=9-1x

y=(500+9x)(9-x)
y=4500-9x^2-500x+81x
y=(-9x^2)-419x+4500

I tried to solve using quadratic formula but my answer was way too large of a number. What did I do wrong?
<pre>One of your binomials should be: 500 + 100x, not 500 + 9x
You should then get: f(x) = (500 + 100x)(9 - x), and subsequently, maximum profit of: {{{highlight_green("$"4900)}}}