# Thread: Show A \ B countable...what is A \ B?

1. ## Show A \ B countable...what is A \ B?

let A an be uncountable set and B a countable subset of A, show A\B is uncountable. I am not familiar with A \ B, and can't find it in the book!

2. Originally Posted by mtlchris
let A an be uncountable set and B a countable subset of A, show A\B is uncountable. I am not familiar with A \ B, and can't find it in the book!
A\B just refers to the set difference. You might've seen $A - B$. A\B $\equiv A - B \equiv A \cap B^c$.

You can refer to Set Difference -- from Wolfram MathWorld