請教-題目為什麼這樣解

htts

龍舌蘭 發表於 12-10-7 22:50
問題及原解如下, 請教為什麼? X2 +4X-2=0   (其中, X2 表示X的二次方, 因打不出來)

解題為: X2 +4X +4-2=4 ...

WOW!  Your girl already known this kind of Maths.  My girl has no idea about it and she has never touched upon this kind of question.