已知集合A={x|x=a+b根号2,a,b∈Q},若X1∈A,X2∈A

令x1=a+b√2x2=m+n√2则(x1*x2)=(a+b√2)(m+n√2)=am+an√2+bm√2+2bn=(am+bn)+(an+bm)√2而am+bn∈Qan+bm∈Q所以x1x2∈Ax1/x2=(a+b√2)/(m+n√2)=(a+b√2)(m-n√2)/(m+n√2)(m-n√2)=(am-an√2+bm√2-2bn)/(m^2-2n^...