... ,0. 7) , (x3,0. 5)} A2= {( y 1 ,0. 4) , (y2,0. 3)} Vậy ta có : ℜ(A 1 , A2 )= {(( x 1 ,y 1 ) , 0. 4) , (( x 1 ,y2 ) , 0. 3) , (( x2,y 1 ) , 0. 7) , (( x2,y2 ), 0. 7) , (( x3,y 1 ) , 0. 5) , (( x3,y2 ) ... = {( (x 1 ,x2 ), μ?ℜ(x 1 ,x2 )) ∣(x 1 ,x2 ) ∊X 1, X2μ?ℜ(x 1 ,x2 )= min{ μ?Q(x 1 ,x2 ) , μ?S(x 1 ,x2 )} }+Phép hợp : Q ⋃S = {( (x 1 ,x2 ), μ?ℜ(x 1 ,x2 )) ∣(x 1 ,x2 ) ∊X 1, X2μ?ℜ(x 1 ,x2 )= max{ ... ⋀μ?B(x).+ Phép hợp:A ⋃B = {(x, μ?∪?(x )) ∣x ∊X, μ?∪?(x)=max{ μ?A(x),μ?B(x)}}Ký hiệu : μ?A(x) ⋁μ?B(x).+ Phép trừ:A-B={(x, μ?A-B(x )) ∣x ∊X, μ?A-B(x)=min{ μ?A(x), 1- ?B(x)}}+...