... (x 2 ,0. 7) , (x3,0. 5)} A 2 = {( y1,0. 4) , (y 2 ,0. 3)} Vậy ta có : ℜ(A1 , A 2 )= {(( x1,y1 ) , 0. 4) , (( x1,y 2 ) , 0. 3) , (( x 2 ,y1 ) , 0. 7) , (( x 2 ,y 2 ), 0. 7) , (( x3,y1 ) , 0. 5) ... {( (x1,x 2 ), μ?ℜ(x1,x 2 )) ∣(x1,x 2 ) ∊X1,X 2 μ?ℜ(x1,x 2 )= min{ μ?Q(x1,x 2 ) , μ?S(x1,x 2 )} }+Phép hợp : Q ⋃S = {( (x1,x 2 ), μ?ℜ(x1,x 2 )) ∣(x1,x 2 ) ∊X1,X 2 μ?ℜ(x1,x 2 )= 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)}}+...