(a²-4/a²-4a+4 - 2/a-2)÷ a²+2a/a-2
=((a+2)(a-2)/(a-2)² - 2/a-2)÷ a²+2a/a-2
=((a+2)/(a-2) - 2/a-2)÷ a²+2a/a-2
=(a+2-2)/(a-2)÷ a²+2a/a-2
=a/(a-2) * (a-2)/a(a+2)
=1/(a+2)
当a=1
上式=1/3
(a²-4/a²-4a+4 - 2/a-2)÷ a²+2a/a-2
=((a+2)(a-2)/(a-2)² - 2/a-2)÷ a²+2a/a-2
=((a+2)/(a-2) - 2/a-2)÷ a²+2a/a-2
=(a+2-2)/(a-2)÷ a²+2a/a-2
=a/(a-2) * (a-2)/a(a+2)
=1/(a+2)
当a=1
上式=1/3