1. The problem statement, all variables and given/known data I'm having a bit of difficulty understanding the unit step function For example f(t) = 6u(-t) + 6u(t+1) - 3u(t+2) t = -1 2. Relevant equations 3. The attempt at a solution If t = -1 then the way I would do the problem is say that if u(t) returns a negative number or zero then it's zero 6(1) + 6u(0) - 3(1) = 3 However, the answer is 9 so I must be misinterpreting how the unit step function works. Can anyone explain to me how one would handle the unit step function in this situation?