怎樣證實這題1+1=2係錯?

你在一開始的假始已出了問題

假設A=B

A^2=AB
A^2 -B^2= AB -B^2
(A -B) (A+B)=B(A -B) <-------------- 這裏 因為(A -B) = 0 所以是不可以相除的
A+B=B
2B=B

就我的知識層面
在數學界
暫時未有一個定義是給予 0 over 0 的

the process from third process to fourth process is wrong.
because if you both side diveded by A-B, it means that diveded by 0, it is wrong.