Quadratic equation
In mathematics, a quadratic equation (from Latin quadratus 'square') is an equation that can be rearranged in standard form as a x 2 + b x + c = 0 , {\displaystyle ax^{2}+bx+c=0\,,} where the variable x {\displaystyle x} represents an unknown number, and a, b, and c represent known numbers, where a ≠ 0. (If a = 0 and b ≠ 0 then the equation is linear, not quadratic.) The numbers a, b, and c are the coefficients of the equation and may be distinguished by calling them the quadratic coefficient, the linear coefficient and the constant coefficient or free term, respectively.