Question 700534
{{{ R(x)=385x-0.9x^2 }}}
If the general form is
{{{ ax^2 + bx + c }}}, then then the 
x-coordinate of the vertex is at
{{{ -b/(2a) }}}
{{{ a = -.9 }}}
{{{ b = 385 }}}
{{{ c = 0 }}}
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{{{ -b/(2a) = -385 / ( 2*(-.9) ) }}}
{{{ -b/(2a) = 385/1.8 }}}
{{{ -b/(2a) = 213.89 }}}
and
{{{ R(max)=385*213.89-0.9*213.89^2 }}}
{{{ R(max) = 82347.22 - 41174.04 }}}
{{{ R(max) = 41173.18 }}}
The maximum revenue is $41,173.18
Here's the plot:
{{{ graph( 400, 400, -100, 500, -5000, 50000, -.9x^2 + 385x ) }}}