先将代数式a^2-1分之a^2-2a+1除以a^2+a分之2a-2化简,再从-1,0,1,2中选取一个适当的数作为a的值

[(a²-2a+1)/(a²-1)]÷[(2a-2)/(a²+a)]=[(a-1)²/(a+1)(a-1)]*[a(a+1)/2(a-1)]=a/2带入a=2得原式=1