Demand
q = 1000 - 2p2
Price
p = p
Revenue
r = pq = p (1000 - 2p2) = -2p3 + 1000p
Find the critical values by taking the derivative
dr/dp = -6p2 + 1000
and then setting the derivative equal to zero
-6p2 + 1000 = 0
6p2 = 1000
p2 = 1000/6 = 500/3
p = ± 10√(5/3)
We can dismiss negative prices as being outside the domain of our problem (and otherwise an unlikely choice to maximize revenue).
p = 10√(5/3) ≈ 16.99