Tìm

- Hướng dẫn giải

a) x $\in$ {0; 1; 2; 3; 4;5;6;7 }               b) x $\in$ {-4; -3; -2; -1}

c) x $\in$ {-3;-2; - l}.                               d) x $\in$ {-5; -4; -3; -2; -1; 0}

e) x $\in$ {-2; -1; 0; 1; 2}                       f) x = $\varnothing$