@robertmarc
That's not going to be a simple solution if it is a video hardware problem.
You need to connect an external monitor to the laptop and see if the blotch appears at the same location on that. IF it does, then the video chip is failing and that can not be replaced. IF it does not, then the laptop screen is faulty -- but while that can be replaced, it is very expensive to do so -- especially if the laptop is no longer under warranty.
Report back what you find out after connecting the external monitor.
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