Question 1195777
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R(x) = {{{10000x-2x^2 }}}
dR/dx = 10000-4x

At min or max, dR/dx = 0:  10000-4x = 0  ==>  x = 2500 units for max revenue. 
You can see this is a max (and not a min) by looking at 2nd deriv. which is -4 ==> concave down ==> critical point is a local maximum.

Plug in x=2500 into R(x) to get the max revenue.  To convince yourself, you should plug in x=2501 and x=2499 to see those R(x) values are less than R(2500).