题目内容
用“<”或“>”填空:如果0<a<b<1,n∈N*,那么________________1.
(1)x∈A∪B,则x∈A_________x∈B;
(2)x∈A∩B,则x∈A_________x∈B;
(3)若ab=0,则a=0_________b=0;
(4)若a2+b2=0,则a=0_________b=0.