數學問題!?唔該幫忙!!!快!!!!

X^(1/2)=-2
X等於幾多?

F幾既數-.- 0.5次方咁得意既``
咁既話`試下兩邊SQUARE``
X^(1/2) = -2
X           = -4

唔該灑.....

[quote]原帖由 [i]{ｃhiｎ}[/i] 於 2006-10-24 10:32 PM 發表
F幾既數-.- 0.5次方咁得意既``
咁既話`試下兩邊SQUARE``
X^(1/2) = -2
X           = -4 [/quote]

sorry-.-你錯了...
-2既square係4-.-..........負負得正.....

1/2次方即係開方, 1/3次方就係立方根...
冇記錯係中3教的

[[i] 本帖最後由 幽魂『Phantom』 於 2006-10-24 11:00 PM 編輯 [/i]]

[quote]原帖由 [i]幽魂『Phantom』[/i] 於 2006-10-24 10:58 PM 發表


sorry-.-你錯了...
-2既square係4-.-..........負負得正.....

1/2次方即係開方, 1/3次方就係立方根...
冇記錯係中3教的 [/quote]
sqrt(x) = -2

then the question MUST be wrong,
since the definition of sqrt is not only ^1/2
if you hv learned function,
x^1/2 is not injective
but sqrt(x) is

或者咁講, 開方係 1/2次方之後取絕對值..

[quote]原帖由 [i]Ｈydro;)[/i] 於 2006-10-28 04:04 PM 發表

sqrt(x) = -2

then the question MUST be wrong,
since the definition of sqrt is not only ^1/2
if you hv learned function,
x^1/2 is not injective
but sqrt(x) is

或者咁講, 開方係 1/2次方之 ... [/quote]

條數冇問題....
唔知係咪你個老師咁教你
但我阿sir一直都係教sqrt一個數一定要consider哂正負2個case
所以如非必要都盡量避免將一個數開方
仲有-.-....樓主冇話呢條數係funchtion....
(聽到injective就開始頭痛了= =)
呢條只係一條equation而已....

第1次聽人講sqrt同1/2次方唔同...
可以詳細少少解釋一下有d咩唔同嗎?

[quote]原帖由 [i]幽魂『Phantom』[/i] 於 2006-10-28 08:51 PM 發表


條數冇問題....
唔知係咪你個老師咁教你
但我阿sir一直都係教sqrt一個數一定要consider哂正負2個case
所以如非必要都盡量避免將一個數開方
仲有-.-....樓主冇話呢條數係funchtion....
(聽到injective就開 ... [/quote]
from wiki

請切換完整版來瀏覽圖片和連結