[tex]A=\{x \in N ~|~2x \ \textless \ 7 \} ~~si~~ B=\{x \in N~|~x \ \textless \ 2\} \\
A=\{0;~1;~2;~3 \} ~~si~~B= \{ 0;~1\} \\
A \bigcup B = \{0;~1;~2;~3 \} = A~~deooarece ~~ B \subset A \\
A\Delta B = (A-B) \bigcup (B - A) = \{2;~3 \} \bigcup \O = \{2;~3 \} [/tex]