两题计算题 1、2/a²-4*[(a²+4/4a)-1] 2、[（a/a-1)-1] /(1/a&#

2/(a²-4)*[(a²+4)/4a-1]
=2/(a²-4)*[(a²+4-4a)/4a]
=2/(a²-4)*(a²-4a+4)/4a
=2/[(a-2)(a+2)]*(a-2)²/4a
=1/(a+2)*(a-2)/2a
=(a-2)/[2a(a+2)]
=(a-2)/(2a^2+4)
[a/(a-1)-1] /[1/(a²-2a+1)]
=[(a-a+1)/(a-1)] /[1/(a-1)²]
=[1/(a-1)] /[1/(a-1)²]
=1/(a-1)*(a-1)²
=a-1