Here is my answer:
step(t-1)-6*step(t-3)+9*step(t-5)
but it's wrong!!
help!!
Note as quick check when you evaluate at you get
Just "turning on" the next part is not enough you need to "turn off" the first part as well.
Let be the unit step function then
Note to fit the turn on and off analogy from above
When you simplify it is the same as above.