**I was Wrong
let X be a metric space and A an open subset of X
Prove that A ∩ B^{−} ⊂ (A∩B)^{−}
My approach:
let x∈A ∩ B^{− }Then x∈A and x∈B^{−}
nbhd(x) intersects A and B for all ε >0
so x∈ A^{−}∩ B^{−}
but (A∩B)^{−} ⊂A^{−}∩ B^{−}
Did I do anything wrong or miss something?