Algebra 2 (1st Edition)

Increasing the price by $100$
$y=(200+10x)(40-x)=-10x^2+200x+8000=-10(x^2-20x)+8000=-10((x-10)^2-100)+8000=-10(x-10)^2+1000+8000=-10(x-10)^2+9000$ Thus the vertex of the graph is at $(10,9000)$, and the shop can maximize its revenue by increasing the price by $\$100\$.