\[\boxed{\text{838.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ a - b = - 0,001\]
\[a < b\]
\[\textbf{б)}\ a - b = 0\]
\[a = b\]
\[\textbf{в)}\ a - b = 4,3\]
\[a > b\]