If in case you have moved the Original files on the hard drive, then you need to update that location in Lightroom catalog so that Lightroom can continuously see your files and let you edit them.
You can refer link for the same: Adobe Photoshop Lightroom Help | Locate missing photos
If you are facing some issue doing the synchronizing the folder after the Lightroom update to the latest version, please follow the link to fix it : Thumbnails display black in Lightroom CC 2015.2/6.2
Let us know if it helps.
I looked tried the links you sent, but they did not solve the problem.
I was careful to make all my changes in Lightroom.
The program should have deleted files and folders on the hard drive when I deleted them in Lightroom.
I always check "Delete From Disk" when I delete files.
Any other reason why it would not work that way?
Please check that you don't have duplicates for same images on your system.
I think I've identified part of the problem. If you use the Remove command on an empty folder from within Lightroom, it is deleted from the hard drive. However, if there is anything in the folder, it is not deleted from the hard drive. I'm not sure why files I moved from one folder to another were duplicated. Can you look at moving files around from this angle?
I have tried performing the above steps as mentioned, it remove only the folder from Lightroom Catalog.
Images on the disk will remains the same including the folder as well.
There must be something else happen on your machine for duplicating the Images.