What characteristic does a quadratic equation have?

A quadratic equation is defined by its highest degree, which is two. This means that it involves at least one variable raised to the second power. In its standard form, a quadratic equation is written as ( ax^2 + bx + c = 0 ), where ( a ), ( b ), and ( c ) are constants and ( a \neq 0 ). The presence of the ( x^2 ) term is what characterizes the equation as quadratic, distinguishing it from linear equations that only involve terms raised to the first power and graph as straight lines.

The other options present ideas that do not accurately describe a quadratic equation. For instance, while a quadratic can have negative coefficients, this does not prevent it from being classified as such. Additionally, a quadratic function typically has two solutions, which can be real or complex, rather than being limited to just one solution. Hence, the correct identification of a quadratic equation is that it involves a variable raised to the second power.