（2014•昆都仑区一模）化简：(1−1a−1)÷a2−4a+4a2−1=a+1a−2a+1a−2．

Question

（2014•昆都仑区一模）化简：(1−(1)/(a−1))÷(a2−4a+4)/(a2−1)=

(a+1)/(a−2)

(a+1)/(a−2)

．

Answer 1

原式=(a−1−1)/(a−1)÷((a−2)2)/((a+1)(a−1))=(a−2)/(a−1)•((a+1)(a−1))/((a−2)2)=(a+1)/(a−2)．
故答案为：(a+1)/(a−2)