Analisis Pemahaman Konsep Pada Materi Barisan dan Deret Berdasarkan Teori APOS (Action, Process, Object, Scheme) di Kelas XI SMK Muhammadiyah Kartasura Tahun Pelajaran 2017/2018

The purpose of the study is to describe the understanding of students' mathematical concepts on sequence and arithmetic series based on APOS theory. The subjects of the study were mathematics teachers and students of grade XI MB SMK Muhammadiyah Kartasura. The research method used is test, interview, and documentation. Data analysis techniques are conducted qualitatively through 3 paths namely data reduction, data presentation, and conclusion. The results showed that students' understanding of this material varies at the stage of action, process, and object. Students who are able to achieve understanding indicator at action stage is 61,11%, process stage equal to 96,29%, at object stage equal to 57,41%, and 44,44% at scheme stage. Students who score above the KKM both are only able to achieve an understanding indicator at the stage of action, process, and object. Students who score under the KKM, both are only able to achieve an understanding indicator at the stage process. At the stage of the scheme, the two have not been able to achieve an understanding indicator. Students at the scheme stage still use manual way to solve the problem. Students have not been able to use the concept of the number of n first tribes correctly