No, it does not.Q1: So does it not matter what the impulse is at n = 5?!
Only for "n" higher or equal to 0, otherwise u[n]=0.Q2: If so, we can then just remove the summation and say:
u[n] = impulse[0] for any index n?!
In the book is written the same, u[n]=summation of impulses, isn't it ? I see no reason for the magnitude symbol here... magnitude symbol makes sense in complex numbers... but I do not see any complex number here. The module symbol on the other hand (i.e. |-3|=3) does not make sense either because there are no negative values in this case.Also, if they just mean the maginitude of u[n] equals the magnitude of the summation of impulses,
Q3: Why don't they use the magnitude symbol:
|u[n]| = |summation of impulses|?
To be a finite sum and hence more easily apply transforms and convolution and etc..Q4: Also, why does the summation stop at n?! We can easily have it upto positive infinity (as the magnitude will still be 1)?!