Hi William,
I'm Rodrigo and I will help you.
If your laptop has an Intel processor, you need to change the graphics settings on Intel Graphics Command Center.
On Intel Graphics Command Center, go to Display and the option you want to change is "Scale", set it to "Stretched"
On my tests, the option "Stretched" does not show unless you have a resolution setting that needs to be stretched, so, if it is not appearing, set a different resolution to the display that has the black bars, change the scale setting to "Stretched", then, set your resolution back.
Now when your resolution changes, it will be automatically set to "Stretched" and fill the whole screen.