A candlemaker prices one set of scented candles at $10 and sells an average of 200 sets each week. He finds that when he reduces the price by $1, he then sells 50 more candle sets each week. A function can be used to model the relationship between the candlemaker's weekly revenue, R(x), after x one-dollar decreases in price. This situation can be modeled by the equation y =
x2 +
x +
and by graph
.