Hello, I am trying to understand the slides in the PDF I posted. I am looking particularly at slides 20-24. I am so confused how the matrices are set up with two separate coefficient conditions. The context of these slides is that we are learning how to interpolate with cubic splines. What is going on with these slides? The professor is incomprehensible to me in the lecture videos due to being overly mathematically rigourous, so I can't figure out what is happening. It's like he is putting a matrix within a matrix. How am I supposed to do that multiplication? Is it like the matrix within the matrix times each vector, or an element of the vector within the inner matrix? So confused... And how is that going to help me with doing cubic polynomial fits within the context of an interpolation?