Write the Word or Phrase That Best Completes Each Statement $f ( x ) = a _ { n } x ^ { n } + a _ { n - 1 } x ^ { n - 1 } + a _ { n - 2 } x ^ { n - 2 } + \ldots + a _ { 1 } x + a _ { 0 }$

Short Answer

Write the word or phrase that best completes each statement or answers the question.
Provide the missing information.
-A function defined by $f ( x ) = a _ { n } x ^ { n } + a _ { n - 1 } x ^ { n - 1 } + a _ { n - 2 } x ^ { n - 2 } + \ldots + a _ { 1 } x + a _ { 0 }$ where $a _ { n } , a _ { n - 1 } , a _ { n - 2 } , \ldots a _ { 1 } , a _ { 0 }$ are real numbers and $a _ { n } \neq 0$ is called aـــــــــ function.