Quadratic equation
In elementary algebra, a
quadratic equation is any equation having the form where
x represents an unknown, and
a,
b, and
c are constants with
a not equal to 0. If
a = 0, then the equation is linear, not quadratic. The parameters
a,
b, and
c are called, respectively, the quadratic coefficient, the linear coefficient and the constant or free term. Because the quadratic equation involves only one unknown, it is called "univariate". The quadratic equation only contains powers of
x that are non-negative integers, and therefore it is a polynomial equation, and in particular it is a second degree polynomial equation since the greatest power is two. Quadratic equations can be solved by a process known in American English as factoring and in other varieties of English as
factorising, by completing the square, by using the quadratic formula, or by graphing. Solutions to problems equivalent to the quadratic equation were known as early as 2000 BC.