Determine an Equation for the Quartic Polynomial Function Represented by the Table of values.

x / y

-3 / 91

-2 / 21

-1 / 3

0 / 1

1 / 3

2 / 21

3 / 91

Can someone please not only help me but explain how I would do a question like this? I'm pretty sure I will see this on my test but need to understand the steps involved in order to complete this question.