This study presents the results of teaching experiment of 7th-grade students about the meaning of the minus sign as the initial knowledge toward the concept of negative integers and its operations. A hypothetical learning trajectory (HLT) was designed on the basis of findings in a preliminary study showing that most students did not understand the meaning of the minus sign that resulted in students' ability in operations involving negative integers. Implementation and revision of HLT were carried out by involving 32 seventh grade students and a math teacher by taking into account the stages of the didactical situation. Furthermore, group learning can encourage students to identify the meaning of minus sign encountered in a context. All data in the form of learning video recording, interview, and students worksheet are analyzed qualitatively based on the perspective of the theory of didactical situation to get the instruction design according to the condition and requirement of the students. The learning practices indicate that the students can differentiate the meaning of the minus sign according to the context of the given problem.
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