Question

#15 I have a test tomorrow and totally forgot how to do this help.

Answer 1

Simple.... just add the values with the corresponding exponent. i.e.
(13n^2+11n-2n^4)+(-13n^2-3n-6n^4)
so you put them together.
the answer would be : 8n - 8n^4

Answer 2

This is the answer unless you want it factored.