​ help!

Let's first look at what it's NOT......!!!

It's not linear because the changes in y's and x's are not uniform

Its not a quadratic because the end behavior would be either up-up  or down-down   ......and the data indicates that this is up-down

It could be a cubic in some form such as : y = -ax^3-bx^2 - cx

i have NO clue

If it's linear the first difference column will be constant,

if it's a quadratic the second difference column will be constant,

if it's a cubic the third difference column will be constant, ..........etc etc