d(x,y) = |x-y| / 1+|x-y|

Describe B1(0), open ball of centre 0 and radius 1;

so i've got (|x| / 1+|x|) < 1

Is that enough of a description? Not sure what I could say about Br(a)

And (X,d) a metric space, fix a point o in X

let d1(x,y)= d(x,o) + d(o,y)

if x ≠ y and d1(x,x)=0

Let x ≠ 0, describe Br(x) w.r.t d1 for all possible r

Not sure at all with that one, any hints would be appreciated.