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標題: A math Problem [打印本頁]

作者: andrew_on 時間: 21/1/2007 05:49 PM
標題: A math Problem
1. Suppose that a=b, then

a*a=a*b
a*a-b*b=a*b-b*b
(a+b)(a-b)=(a-b)b
(a+b)=b both sides are divided by (a-b)
b+b=b
2b=b
2=1 both sides are divided by b

But 2 aren't equal to 1, what's wrong?

Please help, I can't figure out.

作者: abc666 時間: 21/1/2007 06:49 PM
我a math 好屎

呢d乜題目黎我未做過ge?

如果唔both sides are divided by (a-b)
變成
(a+b)(a-a)=(a-a)b
(a+b)(0)=(0)b
0=0 得唔得?

作者: zubat 時間: 21/1/2007 07:33 PM

原帖由 魔術師Chikorita 於 21/1/2007 18:01 發表

這兒錯了
a^2-b^2=(a+b)(a-b)

沒錯啊
a*a不就是a^2嗎?

問題在"both side divided by (a-b)"
because a=b, (a-b)=0
除以0會變成undefined

作者: andrew_on 時間: 21/1/2007 09:38 PM

原帖由 zubat 於 21/1/2007 19:33 發表

沒錯啊
a*a不就是a^2嗎?

問題在"both side divided by (a-b)"
because a=b, (a-b)=0
除以0會變成undefined

Wow
Thank you
You are very clever

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