Answer:
193.77 < p < 1806.23
Explanation:
You want R(p) > 2,100,000, so ...
-6p^2 +12000p > 2100000
p^2 -2000p < -350000 . . . . divide by -6
Adding (2000/2)^2 = 1000000 will "complete the square".
p^2 -2000p +1000000 < 650000 . . . . complete the square
(p -1000)^2 < 650000
-√650000 < p -1000 < √650000 . . . . take the square root
1000 -806.23 < p < 1000 +806.23 . . . .add 1000
193.77 < p < 1806.23 . . . . range of prices for desired revenue