Cho hai tập A={1;-2;4} và B={-4;-3;0;8} a. Viết tất cả các phân số mà tử số là một phần tử của A và mẫu số là một phần tử của B. b. Đưa các phân số trên về dạng có mẫu dương. c. Tìm các phân số bằng nhau trong các phân số trên

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