摘要：This study aims to: 1) develop learning media based on discovery learning models that are valid, practical, and effective; 2) Analyzing learning media that can improve students' mathematical reasoning so that students easily understand it in the learning process. This research includes development research, using a 4-D centered development model to develop mathematical learning media on row and series material. Based on the results of the validity of instructional media according to the experts fulfilled the valid criteria of all indicators 0.81, the results of the first try out of practicality by the experts met the criteria of quite practical 79.7% and the results of the second trial had met the practical criteria of 85.2%, the results the first phase of effectiveness tested in the X-MM class of Istiqlal Deli Tua Vocational School did not meet the completeness criteria while the second trial met the completeness criteria. The results of the analysis of the data obtained show that discovery learning-based learning media meet valid criteria, test the feasibility of the application of practical and effective learning media and can improve students' mathematical reasoning abilities. The results of the study are recommended that practical and effective trials on learning media developed to be better carried out on different samples and used for all students at the same level.
