已知对于任意的ε>0无论它有多么小)有|a-b|

Question

已知对于任意的ε>0无论它有多么小)有|a-b|

Answer 1

用反证法,Assume a is not equal to b then |a-b|>0 let |a-b| = c where c >0choose ε = c/2|a-b| = c < c/2 ( contradiction c >0 )so "a is not equal to b" is wrong=> a=b