? ????????? , ????? ????? ????? ????? r {\displaystyle r} ??? ????? ?????? − r {\displaystyle -r} ?????? r + ( − r ) = 0 {\displaystyle r+(-r)=0} .
??? ???? ???? r {\displaystyle r} , ?????? r ⋅ ( − 1 ) = − r {\displaystyle r\cdot (-1)=-r} .
???? ????? ??? ???? ?? ???? ????? ???? ????? . ????? ????? ?????? ?? ???? ????? .