- #1

- 295

- 4

## Homework Statement

Consider the following problems

In #2, they start the solution by saying: r(t)=u(t-1)

in #3, they start by saying that r(t)=t-tu(t-1)

I understand how to solve the problem once you get r(t), I just don't understand how they decide what r(t) is going to be.