Question 423912
{{{ y = -2.5x^2 + 22.5x + 50 }}}, x = number of years since 1998.
In 1999, x = 1, so there were -2.5 + 22.5 + 50 = 70 stores
For 2004, x = 2004 - 1998 = 6 years.
Putting this into the equation gives -2.5*6^2 + 22.5*6 + 50 = 95 stores
Therefore, there were 95 - 70 = 25 more stores operating in 2004 than in 1999.
Note that the number of stores peaks at x = 4.5 years. After that the number of stores starts to decline.  
At the end of the 10 years, they actually have less stores than when they started!
This is the graph of the equation:
{{{graph(300,200,-20,20,-100,100,-2.5x^2+22.5x+50)}}}