# Thread: Summation question and properties

1. ## Summation question and properties

$y[n] = \sum_{m=-\infty}^{n} x[n]$.

I need to be able to solve this in order to figure some properties of the function

I actually have no clue what to do when I have negative infinity at the bottom.

I'd really like to know how to do this and these kinds of summations since my course on signals depends on knowing how to solve these.

anyways my idea would be somehow trying to get this summation to start from 0 instead of negative infinity

2. Originally Posted by akhayoon
$y[n] = \sum_{m=-\infty}^{n} x[n]$.

I need to be able to solve this in order to figure some properties of the function

I actually have no clue what to do when I have negative infinity at the bottom.

I'd really like to know how to do this and these kinds of summations since my course on signals depends on knowing how to solve these.

anyways my idea would be somehow trying to get this summation to start from 0 instead of negative infinity
With respect to M what you have are 2 constants. So,

$\sum_{m=-\infty}^{n} x[n] = XN \sum_{m=-\infty}^{n} 1$

Unless you have a subscript M on your x that you didn't put in?