x²-5x+6=0 (x-2)(x-3)=0 x=2或x=3 A={2,3}
x²-(2a+1)x+a²+a=0 (x-a)[x-(a+1)]=0 x1=a或x2=a+1
∵x1≠x2 ∴a=2,a+1=3
∴a=2