Non linear algebric equations

Hello everybody,
I’m a new Mathematica user therefore I have not practice with this software. I need solving a non linear algebric system and I know only the solution range. In the last week i used Nsolve and FindRoot function but the results were not correct. I know the range of the variables solution is 0-1. Can I choice the range of the Nsolve solution?

Thank you very much

Put in a constraint 0 <= variable <= 1