Hello,
How can i copy that formula ?
cauhoi.odt
Please retag your question to replace common with writer because your question is a Writer one. This is the official tag for Writer questions. libre-writer does not fulfill the same purpose (it is an erroneous tag created someday by a user and it perpetuates itself).
Copy the whole cell: drag from that cell to the next one then back until just the that cell is selected entirely, copy.
Click in the cell below and paste. Note that it is quicker to select all the remaining cells and just paste once
Cheers, Al