A quartic function is a function of the form f(x) = ax4 + bx3 + cx2 + dx + e with nonzero a; or in other words, a polynomial function with a degree of four.
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.
Finding Roots: See Quartic equation.
