MathDB
ASU 194 All Soviet Union MO 74 |ax+by+cz|+|bx+cy+az|+|cx+ay+bz|=|x|+|y|+|z|

Source:

July 4, 2019
algebraequation

Problem Statement

Find all the real a,b,ca,b,c such that the equality ax+by+cz+bx+cy+az+cx+ay+bz=x+y+z|ax+by+cz| + |bx+cy+az| + |cx+ay+bz| = |x|+|y|+|z| is valid for all the real x,y,zx,y,z.