A **quadratic function** is a polynomial function in the form

- $ f(x) = ax^2 + bx + c = 0,\quad a \ne 0 $

The graph of a quadratic function is a parabola. If $ a = 0 $, the function becomes linear. $ ax^2 + bx + c $ is a second degree polynomial, as the highest exponent of $ x $ is 2. When the function is set to equal zero, it is called a quadratic equation. The solutions to the equation, called roots (zeros) correspond to x-intercepts on a graph. They can be found by factoring, completing the square, graphing, or the quadratic formula.

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