I am your student, Anthony from MATH 2568. May I ask are the answers for question 12 are t = 5, t = 5, t = 15, and t = -1 , which is (t-5)^2(t-15)(t+1)=0? I can find the answers in textbook (Exercise 4.5), but it is (t+5)^2(t-15)(t+1)=0 which is different from mine. Therefore, I wonder is there an error with the answer?
Hope to hear back from you soon.