(1/infinity)-(1/infinity) will equal, (1*infinity-1*infinity)/infinity which is intermediate.
While (1-1)/infinity is simply 0/infinity, which is simply 0 !
However
(0/infinity-0/infinity) shall equal, (infinity*0-infinity*0)/(infinity*infinity) which is indeterminate.
(1/infinity)-(1/infinity) will equal, (1*infinity-1*infinity)/infinity which is intermediate.
While (1-1)/infinity is simply 0/infinity, which is simply 0 !