1. ax² + bx + c = 0, where a, b, c are real numbers, a ≠ 0.
1. Discrimination (D) = b² – 4ac 2. Two distinct real roots, if b² – 4ac > 0, 3. Two equal real roots, if b² – 4ac = 0, 4. No real roots, if b² – 4ac < 0. 5.