The material on page 35 is classic, well-explained, and essential. However, modern readers should supplement it with a discussion of computational methods (since no one solves normal equations by hand anymore) and a warning about overfitting. As part of the whole book, this section remains a gold standard for teaching econometric forecasting—it just shows its age slightly in the absence of simulation-based intuition. Read page 35 carefully, but immediately follow it by working through the same derivation using a small dataset in Python, R, or Stata. The algebraic steps are necessary for theory, but hands-on computation will solidify the concept of "minimizing squared residuals" much faster.