Răspuns :
AUB={1,2,3,4,5,6,7}
AÎ B={3,4}
AÎ {5,6,7}=mult. vida=>{5,6,7} nu apartine mutimii A =>A={1,2,3,4,5,6,7}\{{5,6,7}
A={1,2,3,4}
BÎ {1,2}=mult vida =>{1,2} nu apartine multimii B=>B={1,2,3,4,5,6,7}\{1,2}
B={3,4,5,6,7}
AÎ B={3,4}
AÎ {5,6,7}=mult. vida=>{5,6,7} nu apartine mutimii A =>A={1,2,3,4,5,6,7}\{{5,6,7}
A={1,2,3,4}
BÎ {1,2}=mult vida =>{1,2} nu apartine multimii B=>B={1,2,3,4,5,6,7}\{1,2}
B={3,4,5,6,7}
Cred ca  acele cifre scrise unul dupa altul , sunt elemente ale multumilor ...
A ∪ B = {1;2;3;4;5;6;7 }  ;  A ∩ B = { 3;4 }  ;  A ∩ { 5;6;7 } = ∅  ; { 1;2 } ∩ B= ∅
                        ↓              ↓                ↓
                    inseamna ca     inseamna ca      inseamna ca
                    {3;4} ⊂ A si       {5;6;7} ⊄ A        {1;2} ⊄ B
                    {3;4} ⊂ B
                   __________________________________________
                                     ⇵
                       A  =  { 1;2;3;4 }  si  B  =  { 3;4;5;6;7; }
A ∪ B = {1;2;3;4;5;6;7 }  ;  A ∩ B = { 3;4 }  ;  A ∩ { 5;6;7 } = ∅  ; { 1;2 } ∩ B= ∅
                        ↓              ↓                ↓
                    inseamna ca     inseamna ca      inseamna ca
                    {3;4} ⊂ A si       {5;6;7} ⊄ A        {1;2} ⊄ B
                    {3;4} ⊂ B
                   __________________________________________
                                     ⇵
                       A  =  { 1;2;3;4 }  si  B  =  { 3;4;5;6;7; }