DEFINTION 2. 80t8 集合 Two sets are equal if and only if they have the same elements. Presented as A=B otherwise a= B A=B分Vx(x∈A+x∈B) 2/24/202111:15PM Deren Chen Zhejiang univS e t s 集合 2/24/2021 11:15 PM Deren Chen, Zhejiang Univ. 6 DEFINTION 2. Two sets are equal if and only if they have the same elements. Presented as A=B otherwise A  B A = B   x ( x  A  x  B)