An equation has as many solutions as the highest exponent.
For example: x^5+2x-3=0 would have a maximum of 5 solutions
Well, you already have the decay model, so just plug that in
Answer:
4z^2+7z
you have to combine the like terms
7z+4z^2+6-6
then becomes
(4z^2) + (7z) + (6-6)
gets you to the simplified version which is
4z^2 +7z