Help Please with polynomials

Question

During a 7-year period, the amounts (in millions of dollars) spent each year on buying new vehicles N and used vehicles U by United States residents are modeled by the equations

 N=−0.028t^3+0.06t^2+0.1t+17

U=−0.38t^2+1.5t+42

where t=1 represents the first year in the 7-year period.      

Write a polynomial that represents the total amount spent each year on buying new and used vehicles in the 7-year period.

Answer 1

The total amount spent is N+U:

-0.028t^3+(0.06-0.38)t^2+(0.1+1.5)t+17+42=

-0.028t^3-0.32t^2+1.6t+59. This is the polynomial.