An equation of the type

$$ax^4+bx^2+c=0,$$

where $a,b,c$ are given complex numbers and $a\neq0$. The substitution $y=x^2$ converts a biquadratic equation into a quadratic equation.

How to Cite This Entry:
Biquadratic equation. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Biquadratic_equation&oldid=31441