Extend Line Using Lengthen Command :
1. Select lengthen command
2. Specify the length / distance
3. Click on the line you want to extend
Extend Line Using Trim Command :
1. Select trim command
2. Click on the limiting line
3. Click on the line you want to extend
Librecad https://librecad.org/
Download librecad (free - opensource) https://librecad.org/#download
Work on windows, linux, mac os
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