If a 0 then the equation is linear not quadratic as there is no ax² term. Because it is a second-order polynomial equation the fundamental theorem of algebra guarantees that it has at least one solution. Ax 2 bx c 0.
In math we define a quadratic equation as an equation of degree 2 meaning that the highest exponent of this function is 2.
For example the quadratic equation uses squares or the second power and is thus quadratic. Its general form is ax 2 bx c 0 where x is the variable and a b and c are constants a 0. In mathematics a quadratic equation is a univariate polynomial equation of the second degree. Understanding the quadratic formula.