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Unit step function

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1. Homework Statement
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. Homework 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?
 

Answers and Replies

G01
Homework Helper
Gold Member
2,649
16
The unit step function, u(x) is 1 at x=0, not 0. This is your problem. Try evaluating you expression, taking this into account, and you should get 9 as your answer.
 

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