Gradient(Slope) Introductory videos on You Tube
Please watch any one of the videos on Gradient (or Slope) of a Line at
1. https://youtu.be/jUC-azOrLNs (8 min 1s)
2. https://youtu.be/zVSq5b3PPfY (6 min 47s)
3. https://youtu.be/ADLoWIxKsyQ (7 min 34s)