[ x-1/a-2a+1]+[2a-a/a-a-2】这里的x平方是不是a平方 [ a-1/a-2a+1]+[2a-a/a-a-2】=[ (a-1)(/a-1)]+[a(2-a/(a-2)(a+1)】 =[ (a-1)(a+1)(/a-1)]-[a(a-2/(a-2)(a+1)】 =[(a+1)/(a-1)]-[a/(a+1)] =[(a+1)-a(a-1)]/(a-1)...