Thank u Rohit. It worked. I do have another basic question for u:
I would like to solve this equation dx/dt=TT/6-2*x^2 after I found the inverse function so now TT is a function of x with domain 0,700. I'm going to use to solve it by using the integrate function.
T = Integrate[1/(TT/6-2*x^2), x] which worked.
and then inverse again to get x function of t by using t = InverseFunction[T].
but plotting of the t does not show anything.
Ezra