( . nullus - ), , , . . 0. . .:

0 = 0 = 0.

., .; ab = 0 , a = 0, b = 0. . .

. (, ,  ..). . 0, + 0 = 0 + = , - . . ; . 0 = 0 = 0. ., , .; ab = 0, a ¹ 0 b ¹ 0, b .

: