Why Does Changing Intervals and Arguments Affect Convolution Integrals?

[nhrock3]

cant understand the red arrow transition
i changes the intervals and i cuts half of the arguent inside the integral
i can't see why
?

regarding the interval change
the H function is 1 in a certain interval
so if they change the integrval then its no longer H inside
because we have taken the '1' part of the H
??

regarding the cutting in half the argument inside the integral
i have no idea

 

[nhrock3]

sorry wrong forum

 

[BNoelCMU]

The reason the integration limits change is because you're convolving two pulses that are only defined from -1 to +1, so the convolution is just 0 for all intervals other than -1 to +1.