Can You Solve This Absolute Value Inequality Proof?

[annoymage]

Homework Statement

l lxl - lyl l =< lx-yl

Homework Equations

n/a

The Attempt at a Solution

how do i proof this? give me a start please, should i use definition absolute values and consider all of the cases? or use triangle inequality(but i can't figure out how)

 

[annoymage]

hey i get it, use x=(x-y)+y