Question 363575
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Hi, 
Re:  Annual Income = I(t) = -0.1t^2+2t where t is time in years
I(t) = -.1t(t - 20)
I(0) = 0 & I(20) = O

I(t) = -0.1t^2+2t  (note: negative coefficient of the squared term)
graph of this parabola opens downward, with a maximum at 10years (0+20)/2 
After 10 years, the income begins to decline. 
{{{graph( 300, 300,-0,25,-25,25,-.1x^2 + 2x+0)}}}