Hints on some homework questions:
Section 1.4 # 71:
(b). Set the equation above equal to 500 and solve for t.
Section 1.6 # 58
Total cost of car A after t years is : 10,000 + 550t + 625t=10000 + 1175t
Total cost of car B after t years is: 12,000 + 600t + 375t=12000 + 975t.