Dear Huynh Trong Khanh,
The form "kārayituṃ" is also found, though rarely, in a few Pali texts, the
regular form being "kāretuṃ" which occurs in the Tipitaka.
Since the primary focus of this group is on the Pali language and its
literature (texts and translations), don't you think the Sanskrit extracts
you have been posting of late are better suited in a forum for learning
Sanskrit?
I think the use of Sanskrit in this group should be to help us better
understand Pali as they are both so closely related. I, myself, regularly
make use of Sanskrit dictionaries to look up the equivalents of Pali words.
It is also interesting to study and compare the native grammar traditions
for both Sanskrit and Pali.
Best wishes,
Jim