How do I proof that this is a metric in R? I've been struggling to proof that: |\frac{x}{

Miguel Reynolds

Miguel Reynolds

Answered question

2022-01-14

How do I proof that this is a metric in R?
Ive

Answer & Explanation

Piosellisf

Piosellisf

Beginner2022-01-15Added 40 answers

One observation is that if |x1+|x|y1+|y||=0 then x,y has to be both positive or both negative. Thus we can consider two different cases.
Case 1: Both positive. Thus we have |x1+xy1+y|=0. In other words, x1+x=y1+y. Now use derivatives if necesary, because f(x)=x1+x is one to one, we have x=y. Alternatively, suggested by Dan, one could just multiply through to have x+xy=y+yx
and thus x=y. (We are allowed to multiply through since neither x nor y were assumed to be negative.
Case 2: Both negative. This is similar to Case 1.
Cleveland Walters

Cleveland Walters

Beginner2022-01-16Added 40 answers

If z=x1+|x| then 1|z|=11+|x|,so x=z1|z|
alenahelenash

alenahelenash

Expert2022-01-24Added 556 answers

Note that |z|=0 if and only if z=0 for zR, i.e., xy+x|y||x|y=0. It suffices to show the quantity |x|yx|y|=0 for all x,y such that the equation holds. This is easy, however; if x,y share the same sign the result is clear. The equation does not hold since the two terms x1+|x|,y1+|y| cannot cancel when added.

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