请问两边同除以x的那一步对不对

楼主， 你这个 9 级是打游戏机得来的吗？？？
我看了3分钟才明白你的等号是怎么得来的。。。。悲哀啊。。。。

( x --> -∞ )lim{ [ ( x^2 - x +1 )^(1/2) - ax - b }
= ( x --> -∞ )lim{ [ ( x^2 - x +1 )^(1/2) + x - b }
= ( x --> -∞ )lim{ [ ( x^2 - x +1 ) - (x - b)^2 /[ [ ( x^2 - x +1 )^(1/2) - ( x - b) ] }
= ( x --> -∞ )lim{ [ (2b-1) * x + (1 - b^2 ) ] /[ [ ( x^2 - x +1 )^(1/2) - ( x - b) ] }
= ( x --> -∞ )lim{ [ (2b-1) * x + (1 - b^2 ) ] /[ [ ( x^2 - x +1 )^(1/2) - ( x - b) ] }
= ( x --> -∞ )lim{ [ (2b-1) + (1 - b^2 ) /x ] /[ - [ (1 - 1/x +1/x^2 )^(1/2) - ( 1/x - b/x^2) ] }
= { [ (2b-1) + 0 ] /[ - [ (1 - 0 +0 )^(1/2) - ( 0 - 0) ] }
= 1 - 2b
= 0
b = 1/2