Math Help - Discrete Time Convolution Integral

Hello Everyone!

I've been stuck on this DT convolution sum for quite sum time, it's because I have not much experience in calculating DT sums. Well here goes:




Now,

Now here, I saw that whenevr we have step functions we can remove them and change the limits of the sum, so I modified the sum to be from n+1 to infinity as:
.
But I think I am very wrong.

Any help would be greatly appreciated!

If you mirror and shift h[n], the limits become:

u[-n-1] is 1 for -n-1 >= 0 => n<=-1. If you mirror and shift that you end up with k-n<=-1 => k <= n-1, hence the upper limit.