The root, x-intercept or zero of function ${\displaystyle f}$ is a number ${\displaystyle x}$ in the domain of ${\displaystyle f}$ such that ${\displaystyle f(x) = 0}$. It is the point at which the function crosses the x-axis. In any polynomial with degree ${\displaystyle k}$ has at least ${\displaystyle k}$ complex roots or less, according to the fundamental thearom of algebra.