先化简,再求值:a²-1/a²+2a+1÷a-1/2a+2- (2a)/a+1,其中a=-1/2
问题描述:
先化简,再求值:a²-1/a²+2a+1÷a-1/2a+2- (2a)/a+1,其中a=-1/2
答
原式=(a+1)(a-1)/(a+1)^2
*2(a+1)/(a-1) -(2a)/a+1
=2-(2a)/a+1
=(2(a+1)-2a)/(a+1)
=2/(a+1)
=2/(-1/2+1)
=4