為甚麼加要用這符號+

古希臘數學家丟番圖用兩數並列代表相加.古印度人在公元三世紀時,用「yu」代表相加.古代中國人用算籌運算,並沒有使用任何數學符號,如要記錄加的意思時,便用文字表達.德國人從十五世紀時用「+」.1608年,德國人克拉維烏斯出版巜代數》,意大利人才開始使用.1637年,其他歐洲國家開始認識「+」.最後「+」得以流行於全世界.

如果你咁樣問的話
我又想問下你點解個一字係要"1"
點解個二字係要"2"

原因得一個:就係有人(前人)定義左佢

you can use other 符號 ga... but other people may not understand what you mean....

it is the same that you use 為甚麼 to express why... if you use 廣告宣傳 to express why, no one would understand what you mean by 廣告宣傳加要用這符號+

it is only a 符號 defined by the previous mathematician or people in the past... if they had use # to represent plus, then we may have

2 # 4 = 6

=P