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Formulas/maths/Quadratic Equations

Quadratic Equations

Quadratic Formula
Gives the roots of the standard quadratic equation ax^2 + bx + c = 0 with a \neq 0.
Discriminant and Nature of Roots
Determines the existence and nature of the roots of a quadratic equation with real coefficients.
Difference of Roots
Gives the magnitude of the difference between the roots of ax^2 + bx + c = 0.
Complex Conjugate Root Theorem
States that non-real complex roots of a real quadratic polynomial always occur in conjugate pairs.
Newton's Sums for Quadratic Equations
Relates the sums of powers of roots of ax^2 + bx + c = 0 for integers n \ge 2.
Vertex and Extremum of Quadratic Function
Gives the turning point coordinates and the minimum or maximum value of y = ax^2 + bx + c.
Condition for Definite Sign of Quadratic
Gives the necessary and sufficient condition for a quadratic expression to be strictly positive everywhere.
Location of Roots: Number Between Roots
Condition for a real number k to lie strictly between the real roots \alpha and \beta.
Conditions for Common Roots
Gives conditions for two quadratic equations to have both roots or exactly one root in common.