Posted by Anonymous on .
Use the Quadratic equation to determine the last day that cowboy hats will be sold.
cowboy hats = 0.4x^2 + 20x + 10
Please help me work through this.

Algebra 
Steve,
assuming x is the number of days,
h(x) is the number of hats sold on day x,
h=0 means no hats sold that day, because all were sold, so that is the last day.
h(x) = 0 when x = [20 +/ sqrt(400+16)]/.8
x = 50.5
so, some time during the 51st day sales went to zero.