Hi @mmcky , I noticed the following sentence is missing in lecture 04_linear_algebra:
The solution is known to be $ \hat x = (A'A)^{-1}A'y $ — see for example chapter 3 of <a href=_static/lecture_specific/linear_algebra/course_notes.pdf download>these notes</a>.
Please find a screenshot for the corresponding place of lecture 04_linear_algebra (left: RST, right: MYST):
