Cubic equation
= Cubic equation
{wiki}
A cubic equation is a <polynomial equation> of <degree of a polynomial> three, $ax^3+bx^2+cx+d=0$, with $a\ne0$. Its three complex <roots of a polynomial>, counted with <multiplicity of a root>, need not all have physical significance in an application; a model often selects a branch by continuity from a known limit.