I think two equations are misplaced in the slides for video 4.3 , the equation (the R(f) = sum() terms, in black font) for L1 should be where L2 is now. and vice versa. The content of the voiceover is correct as far as I remember.
And as far as I know, L1 = sum of the absolute values, L2 = sum of the squares. Thhe video has these switched at this time.
This holds for the two slides at 5.58 and 6:22 of the 7:57 video.
