Hi,
It can be a bad display for starters. Connect an external display and see if you'll get any display from it because if you do that means it's the built in display that has a problem. If these doesn't work do try some of these troubleshooting steps that may help.
- Do a hard reset, remove the battery and AC adapter then press and hold the power button for 20 seconds. Plug just the AC adapter then power the laptop.
- Next is to reseat the RAM's, take them all off for couple of seconds then put them back in making sure that they are seated properly.
- Also do test another AC adapter it maybe an issue with it as well.
- If all these doesn't work it's a problem with the motherboard.