find a counter example?
hmm
|a-b| finds the distance between a and b,
|a|-|b| finds the distance between a and b, such that |a|>|b|
ah ha
so we just need to find a and b such that b>a
b=10
a=5
|a-b|=|5-10|=|-5|=5
|a|-|b|=|5|-|10|=5-10=-5
5≠-5
tada
it is not true for all real numbers
if for all numers such that b>a, it is false
