This book presents four topics related to undergraduate courses, typically not covered in standard lectures. Written in a clear and careful style, these four "pearls" aim at complementing and deepening the knowledge of students and instructors by presenting a variety of techniques and useful methods. The first chapter provides a detailed discussion of real numbers, the foundation of any mathematical construction. Chapter two of the book is dedicated to the study of sequences defined by recurrence relations. The third chapter explores certain problems in asymptotic analysis, and the final chapter of the book discusses mathematical results related to "Integration in Finite Terms". Each chapter of the book is accompanied by its respective bibliography. The book is intended for readers with a level of maturity typically attained after completing a bachelor's degree in mathematics.