Can anyone explain: Let $B$ be a Borel set and $B + a = \{ x + a : x \in B\}$. Why is $B + a$ a Borel set?
I think I have to use some good set principle but not sure how to complete the proof.
Can anyone explain: Let $B$ be a Borel set and $B + a = \{ x + a : x \in B\}$. Why is $B + a$ a Borel set?
I think I have to use some good set principle but not sure how to complete the proof.