Tìm x biết

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Bài 3: Tìm x biết:
1) 2x³ - 50 = 0
2) 3x³ - 6x² = 0
3) 4x² - 49 = 0
4) x(x - 3) + x - 3 = 0
5) 2(x(x - 4) + x - 4 = 0
6) (x - 2)(3x + 3) = (x - 2)(2x - 1)
7) x² + 4x + 4 = 16
8) x² - 4 = 2(x² + 4x + 4)
9) (5x - 1)² = (3x + 2)²
10) x² - 6x + 9 = x - 3
11) x² - 2x - 15 = 0
12) 3x² - 2x - 1 = 0