Question 1152648
maximum years would be where x=-b/2a or -18/-6 or x=3

put that into the equation to get p(3)=-27+54-4=23 hundreds of thousands.

from year 3 on, the profit decreases
the zero point is where f(x)=0
this is -3x^2+18x-4=0
or 3x^2-18x+4=0
quadratic formula
x=(1/6)(18+/-sqrt(324-48)); sqrt 276=16.61
x=(34.61/6)=5.77 years, so 2.77 years of decreasing profits.


{{{graph(300,300,-10,10,-10,30,-3x^2+18x-4)}}}