化简求值a2-1/a2-a-2除以a/2a-4,其中a=1/2
问题描述：
化简求值a2-1/a2-a-2除以a/2a-4,其中a=1/2
答
(a²-1)/(a²-a-2)÷a/(2a-4)
=(a-1)(a+1)/[(a+1)(a-2)]x2(a-2)/a
=2(a-1)/a
=2-2/a 把a=1/2代入
=2-4
=-2