biquadratic adj : of or relating to the fourth power

1 an algebraic equation of the fourth degree [syn: biquadrate, quartic, fourth power]

2 an equation of the fourth degree [syn: biquadratic equation]

3 a polynomial of the fourth degree [syn: biquadratic polynomial, quartic polynomial]

English

Adjective

1. Of a polynomial expression, involving only the second and fourth powers of a variable, as x4 + 3x2 + 2. Sometimes extended to any expression involving the fourth power of variable (but no higher powers), as x4 − 4x3 + 3x2 − x + 1.

Related terms

• quadratic
• quartic

A quartic function is a function of the form

f(x)=ax^4+bx^3+cx^2+dx+e \,

with nonzero a; or in other words, a polynomial function with a degree of four. Such a function is sometimes called a biquadratic function, but the latter term can occasionally also refer to a quadratic function of a square, having the form

ax^4+bx^2+c \,,

or a product of two quadratic factors, having the form

(ax^2+bx+c)(dy^2+ey+f) \,.

Since a quartic function is a polynomial of even degree, it has the same limit when the argument goes to positive or negative infinity. If a is positive, then the function increases to positive infinity at both sides; and thus the function has a global minimum. Likewise, if a is negative, it decreases to negative infinity and has a global maximum.

The derivative of a quartic function is a cubic function.

On finding the roots, see Quartic equation.