Question

计算；（x-1)[1-(x+1)除以（x-1/x)]

Answer 1

x-1/x不等于0 ==>x不等于0,-1,1

原式=(x-1)[1-(x+1)/(x^2-1)/x]=(x-1)[1-x(x+1)/(x^2-1)]=(x-1)[1-x/(x-1)]=x-1-x=-1