However, without the exact PDF or page reference, I can identify the most likely from that book: "Reduction of order" or "simplification via integrating factors / exact equations" — but more specifically, De La Fuente emphasizes:

If you ask a mechanical or electrical engineering graduate from schools like Mapúa, UST, or UP (University of the Philippines), many will mention Dela Fuente's notes. The reason is not that the math is different, but that the instructional design respects the student's time.

Covers higher-order linear equations (homogeneous and non-homogeneous), Laplace Transforms , Gamma functions, mathematical series, and matrices. Key Characteristics Step-by-Step Methodology:

Whether you are cramming for a board exam, struggling with your homework, or an instructor looking for a clear teaching aid, tracking down this PDF is worth the effort. Use it to learn the how of DEs, then use other texts to learn the why .