解
[2a/(a-1)+a/(1-a)]/a
=[2a/(a-1)-a/(a-1)]/a
=(2a-a)/(a-1)/a
=a(a-1)÷a
=a-1
=√2+1-1
=√2你的第三步和第四步有没有问题=[(2a-a)/(a-1)]/a=[a/(a-1)]÷a=1/(a-1)=1/(√2+1-1)=1/√2=√2/2