Is 2rs+s^4 a polynomial or not a polynomial?

What situation is an example of an observational study

Marla bought a book for $12.95, a binder for $3.49, and a backpack for $44.99. the sales tax rate is 6%. find the amount of tax and the total she paid for these items

Which of the following is the explicit rule for a geometric sequence defined a recursive formula of a -5a for which the first term is 23?