Find the max of these differential equations

find the max of these equations without solving them. I know that sounds weird, but without going through the calculations, find the max.

y' = 1500 - 3y^2
y' = 1200 - 2y^2

thanks for the help!

y' = 0

1500 - 3y^2 = 0
1500 = 3y^2
500 = y^2
y = +/- sqrt(500)
y = +/- 10 * sqrt(5)

y' = 1200 - 2y^2
2y^2 = 1200
y^2 = 600
y = +/- 10 * sqrt(6)

Do you know what math needs in order to be done? Calculations.