There is one step that I did not get in the following proof I found.
Let Xn be a sequence of real numbers. If Xn is Cauchy then the sequence is bounded.
Given 1 there exist N such that for all n>=N, |xn-xN|<1.
It follows that|xn|<=|xN|+1.
Let b the maximum of |x1|,...,|xN|,|XN|+1. Then b is a bound for the sequence.
I am facing troubles understanding how did you get from |xn-xN|<1 to |xn|<=|xN|+1
Any hint will be very appreciated !!