4/(a²-4)+1/(2-a)
=4/[(a+2)(a-2)]-1/(a-2)
=[4-(a+2)]/[(a+2)(a-2)]
=(2-a)/[(a+2)(a-2)]
=-1/(a+2)
=-1/(2012+2)
=-1/2014
明白请采纳,
有新问题请求助,