证明1)若x∈(A-B)-C,则x∈(A-B)且x∉C,即x∈A,x∉C,x∉B=>x∈A-C,x∉B-C,x∈(A-C)-(B-C)2)若x∈(A-B)-(B-C),则x∈A-C,x∉B-C则x∈A,x∉C,x∉B-C则x∈A,x∉...