The study aims to produce student activity sheets (LAS) square equations based on valid and practical and look at potential effects on students' problem-solving abilities. The type of research used is development research, which consists of two stages, namely preliminary study (preparation stage, analysis stage and design stage) and formative study (evaluation and revision stage) which consists of self-evaluation, expert reviews, one to one, small group and field test. The data collection techniques used in this study are validity questionnaire, practicality questionnaire, interviews and test. The validity questionnaire was analyzed descriptively quantitatively, the practicality questionnaire was analyzed using the Likert's scale score, the interviews were analyzed descriptively and the tests were analyzed by giving an assessment score to the students' answers. The validity of the activity sheet can be seen from three aspects, namely the content, construct, and language contained in the validation sheet at the expert review stage and based on comments / suggestions from the results of the one to one trial. The practicality of the student activity sheet can be seen from the results of the calculation of the given questionnaire and based on observations at the small group stage and see the potential effects of students' problem-solving abilities at the field test stage. From the results of the expert validation sheet obtained an average percentage of 84.9% which includes quite valid criteria and from the results of practicality questionnaire obtained an average percentage of 83.75% which includes practical criteria. Based on expert review validation and one to one and small group trials, valid and practical student activity sheets are obtained. LAS developed also has a potential effect on problem-solving ability judging from the overall test results learners can solve the test questions given.