<![CDATA[Abstrak: Penelitian ini bertujuan untuk mengembangkan dan menghasilkan bahan ajar matematika berbasis GeoGebra yang memenuhi kriteria valid, praktis, dan efektif, serta menganalisis dampak penggunaan bahan ajar terhadap kemampuan pemahaman konsep siswa. Metode penelitian yang digunakan adalah penelitian dan pengembangan (Research & Development/R&D) dengan model Tessmer tipe evaluasi formatif. Subjek dalam penelitian ini terdiri atas 22 siswa kelas VIII A SMP Negeri 2 Latambaga. Teknik pengumpulan data meliputi observasi, wawancara, angket, tes (soal), dan dokumentasi, sedangkan teknik analisis data yang digunakan adalah analisis deskriptif kualitatif. Hasil penelitian menunjukkan bahwa persentase validitas bahan ajar menurut ahli materi dan ahli media mencapai 87,17%. Sementara itu, tingkat praktikalitas berdasarkan penilaian kelompok one-to-one adalah 84,29%, dan dari kelompok small group sebesar 87,62%. Sebanyak 81,82% siswa mencapai ketuntasan dengan KKM 70, dan rata-rata nilai post-test siswa adalah 74,75, yang menunjukkan respons positif terhadap bahan ajar. Simpulan penelitian ini adalah bahan ajar matematika berbasis GeoGebra yang dikembangkan telah memenuhi kriteria valid, praktis, dan efektif, serta memberikan dampak positif terhadap peningkatan kemampuan pemahaman konsep fungsi siswa. Kata kunci: bahan ajar, GeoGebra, pemahaman konsep Abstract: This research aimed to develop and produce GeoGebra-based mathematics teaching materials that meet the criteria of validity, practicality, and effectiveness, as well as analyze the impact of using these teaching materials on students' conceptual understanding abilities. The research method used is research and development (Research & Development/R&D) with the Tessmer model formative evaluation type. The subjects in this study consisted of 22 students of class VIII A of SMP 2 Latambaga. Data collection techniques include observation, interviews, questionnaires, tests (questions), and documentation, while the data analysis technique used is qualitative descriptive analysis. The study results showed that the percentage of validity of open teaching materials according to material experts and media expertsreached 87.17%. Meanwhile, the level of practicality based on one-on-one group assessment was 84.29%, and it was 87.62% from small groups. 81.82% of students achieved completion with a Minimum Mastery Criteria (MMC) of 70 and an average student posttest score of 74.75 which showed a positive response to the teaching materials. This study concludes that the GeoGebra-based mathematics teaching materials developed have met the criteria of being valid, practical, and effective, and positively impacting students' abilities in understanding the concept of functions. Keywords: teaching materials, GeoGebra, conceptual understanding]]>
