Grade 11 math help? Quadratic functions?

A sporting goods store sells reusable water bottles for 8 dollars. At this price their weekly sales are about 100 items. Research says that for every

A sporting goods store sells reusable water bottles for 8 dollars. At this price their weekly sales are about 100 items. Research says that for every 2 dollar increase in price the manager can expect to sell five fewer bottles. Represent the situation with a quadratic function. What is the maximum revenue? What price will give that maximum revenue?

or:A sporting goods store sells reusable water bottles for 8 dollars. At this price their weekly sales are about 100 items. Research says that for every 2 dollar increase in price the manager can expect to sell five fewer bottles. Represent the situation with a quadratic function. What is the maximum revenue? What price will give that maximum revenue?

or:Let x be the number of 2 dollar increases, which will be also the number of 5 items sold decreases. f (x) will represent the revenue:f (x) = (2x + 8)( -5x + 100)This function has its maximum, where its first derivative equals zero.f '(x) = 2( -5x + 100) - 5(2x + 8)f '(x) = -20x + 160- 20x + 160 = 0x = 8So, if you perform the 2 dollar increase 8 times, the bottle will be sold for (2 * 8 + 8) = 24 dollar.And, according to research, there will be sold( -5 * 8 + 100) = 60 items.The revenue equals the product of these two terms:(2 * 8 + 8)( -5 * 8 + 100) = 1440 dollars.

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