Re: [轉錄][新聞] 30÷2(2+3)÷5是多少? 計算機딠…
※ 引述《nanogiant (奈米巨人)》之銘言:
: 綜合以上的文章看起來 歸納一下得到
: 1.乘號省略是在代數運算的表示法
: 2.30÷2(2+3)÷5這個算式中沒有代數 所以是純數運算
: 小弟脫離數學已久 有錯請指證 感謝~
: 我的看法是 30÷2(2+3)÷5這個算式既然是純數運算 那乘號不能省略
: 因此30÷2(2+3)÷5本身是一個錯誤的算式表示法
: 以前學邏輯的時候好像有學到一個概念
: 若命題錯誤 則結果為真 (是這樣表示嗎?)
: 所以不管是把2(2+3)中間補上乘號 還是把2視為係數 都是對的
: 因為30÷2(2+3)÷5這個算式本身就有問題
: 所以爭論15和0.6哪個是正確的唯一解 本來就不會有共識了...
某篇推文有討論到
就算是純數運算
應該也有係數的觀念
但是之後就沒下文了?
30÷2(3)
30÷2cos2
_
30÷2√2
第一眼看到會先做哪部份?
經過思考之後的正確答案又是什麼?
==
再來
"2n是兩個n、是2×n省略乘號的結果"
是國中國小老師教我們的
大家也把它當真理背下來
但是我覺得這是一種"歸納"後的結果
第一個數學家這樣寫了
第二個數學家這樣寫了
大家都這樣寫
於是老師用一句話簡單的教我們應該怎麼寫、怎麼看
想想這個吧
1 1
"2--- 是二又二分之一、是2+---省略加號的結果"
2 2
1
但是我們在做30÷2---的時候
2
會這樣做嗎?
1 1 1 1
30÷2---=30÷2+---=15+---=15---
2 2 2 2 #
所以我懷疑根本沒有一條規定說
"2n是2×n省略乘號的結果"
這只是老師為了自己方便教所產生的句子而已
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討論串 (同標題文章)
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