viết công thức toán $x^2-x-9=0$ [wp_quizjson] { “question_type_id”: “Giải tích 12”, “questions”: [ { “type”: “mcq”, “question”: “Tính tích phân \\(\\int_0^1 x^2 dx\\)”, “option_a”: “$\\frac{1}{2}$”, “option_b”: “$\\frac{1}{3}$”, “option_c”: “$\\frac{2}{3}$”, “option_d”: “$1$”, “correct_option”: “B”, “explanation”: “$\\int_0^1 x^2 dx = \\left[\\frac{x^3}{3}\\right]_0^1 = \\frac{1}{3}$”, “difficulty_level”: “medium”, “is_dynamic”: false }, { “type”: “mcq”, “question”: “Đạo hàm của $f(x) = […]