dau coroqna va rog mult si dau puncte.va rog urggent​

Explicație pas cu pas:

ex 12. A={1, 3,4}

B={1,3,2}

ex 13. A={3,4, 1,2}

B={3,4,5,6,7}

[tex]\it A\cup B=\{1,\ 2,\ 3,\ 4\} \Rightarrow A\subset \{1,\ 2,\ 3,\ 4\}\ \c si\ B\subset \{1,\ 2,\ 3,\ 4\}\\ \\ 2\not\in A \Rightarrow A\subset \{1,\ 3,\ 4\}\ \ \ \ \ (1)\\ \\ A\cap B=\{1,\ 3\} \Rightarrow \{1,\ 3\}\subset A\ \c si\ \{1,\ 3\}\subset B\ \ \ \ \ (2)\\ \\ (1),\ (2) \Rightarrow A=\{1,\ 3,\ 4\},\ \ \ B=\{1,\ 2,\ 3\}\\ \\ Sau:\ \ A=\{1,\ 3\},\ \ B=\{1,\ 2,\ 3,\ 4\}[/tex]