a=(2-√3)/(2+√3)(2-√3)=2-√3原式=(1-a)^2/(a-1)-(√((a-1)^2))/a(a-1) =-(1-a)^2/(1-a)-|a-1|/a(a-1) a-1小于0 =a-1+(a-1)/a(a-1) =a-1+a =2a-1 =3-2√3
