Quadratic equation is a polynomial equation of the second degree. The general form is ax2 + bx + c = 0 where a â‰  0. (For a = 0, the equation becomes a linear equation.)

The letters a, b, and c are called coefficients: the quadratic coefficient a is the coefficient of x2, the linear coefficient b is the coefficient of x, and c is the constant coefficient, also called the free term or constant term.