# Are the definitions of convolution here contradict each other?

Here are two definitions from a lecture slides file from the internet:

It looks strange that the first uses x-u and the second uses x-u+1. Are they both correct? I am confused.

• The vector definition is probably assuming that indexing starts at $1$ rather than $0$. – AnonSubmitter85 Mar 3 '14 at 12:57
• ..., so that the first term $a_1b_1$ gets assigned to $c_1$. Then $a_1b_2+a_2b_1=c_2$ etc. – Lutz Lehmann Mar 3 '14 at 13:16