\[\boxed{\text{900.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ A = \left\{ 1;2;3;4 \right\},\ \ \]
\[B = \left\{ 1;2;3;6 \right\}\]
\(A \cap B = \left\{ 1;2;3 \right\}\)
\[A \cup B = \ \left\{ 1;2;3;4;\ 6 \right\}\]
\[\textbf{б)}\ A = \left\{ Г;Е;О;М;Т;Р;И;Я \right\}\]
\[B = \left\{ Г;Е;О;Р;А;Ф;И;Я \right\}\]
\[A \cap B = \left\{ Г;Е;О;Р;И;Я \right\}\]
\[A \cup B =\]
\[= \left\{ Г;Е;О;М;Т;Р;И;Я;А;Ф \right\}\]