作者奶油銓

(1) 先回答關於 12*8 的問題， 我們先看看乘法的定義是什麼

-----底下是擷取數論的書 ------- (或者找字典的乘法也一樣有類似的定義) ------
Definition of Multiplication. ab is defined on a case-by-case basis.
Case I. b = n is a positive. Then a × n is defined by induction:
(i) a × 1 = a,
(ii) Each a × (n + 1) = a × n + a.
Case II. b = −n is negative. Then a × (−n) is defined to be −(a × n).
Case III. b = 0. Then a × 0 = 0
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上面(ii) 告訴我們 ax(n+1) 這個乘法算式，它背後的定義是有 (n+1) 個 a 相加

字典通常會這樣寫

mul·ti·pli·ca·tion [muhl-tuh-pli-key-shuhn] Show IPA
noun
1.
the act or process of multiplying or the state of being m...