While it is possible that you have received 3 bad inverters, it is unlikely. The bulb on the inside of the screen itself could be failing. If the bulb is bad/failing, the screen will need to be replaced. A decent computer repair shop will be able to tell you the problem is with 1) The inverter, 2) The backllight/screen, or 3) The motherboard.
great thanks i guess i only have the bulb or the mother board problem to worried about i am waiting for my third replacement after that I'm going to the shop it suck because they charge $50 just to diagnose the problem and they still cant tell me exactly what it is. thank you so much