# quadratic

In general the term ‘quadratic’ refers to something involving a square, or the squaring of values, especially formulas or equations with squared terms.

### Algebra/Calculus/Precalculus

A quadratic polynomial is a function of the form

\[p(x) = ax^2 + bx + c\]

where \(a\), \(b\), and \(c\) are real constants with \(a\neq 0\). The roots of a quadratic polynomial may always be found via the *quadratic formula*:

\[x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}\]

The expression under the radical is called the *determinant*. If the determinant is positive, both solutions are real; if negative, both solutions are complex; and if zero, there is a single solution of multiplicity two.

The graph of a quadratic is a parabola, and if the roots are real they correspond to intercepts of the parabola on the \(x\)-axis.

- [MLA] “quadratic.”
*Platonic Realms Interactive Mathematics Encyclopedia.*Platonic Realms, 27 Mar 2013. Web. 27 Mar 2013. <http://platonicrealms.com/> - [APA] quadratic (27 Mar 2013). Retrieved 27 Mar 2013 from the
*Platonic Realms Interactive Mathematics Encyclopedia:*http://platonicrealms.com/encyclopedia/quadratic/