Question 677120
The most albums are sold on the day in which the quadratic has a maximum value. At the maximum value da/dt = 0:
da/dt = 0 = -180t + 8100
Solving for t gives t = 45 days
The maximum number is a(45) = -90*45^2 + 8100*45 = 182,250
These results can be seen by graphing the function
{{{graph(300,300,-100,100,-10000,200000,-90*x^2+8100*x)}}}