式1: 3 "x" plus "y" plus "z" less than 3 left brace, 3 "x" minus "y" minus "z" less than 3 , right brace left brace, negative 3 less than 3 "x" minus "y" plus "z" , right brace left brace, negative 3 less than 3 "x" plus "y" minus "z" , right brace left brace, "x" plus 3 "y" plus "z" less than 3 , right brace left brace, "x" minus 3 "y" minus "z" less than 3 , right brace left brace, negative 3 less than "x" minus 3 "y" plus "z" , right brace left brace, negative 3 less than "x" plus 3 "y" minus "z" , right brace left brace, "x" plus "y" plus 3 "z" less than 3 , right brace left brace, "x" minus "y" minus 3 "z" less than 3 , right brace left brace, negative 3 less than "x" minus "y" plus 3 "z" , right brace left brace, negative 3 less than "x" plus "y" minus 3 "z" , right brace3x+y+z<33x−y−z<3−3<3x−y+z−3<3x+y−zx+3y+z<3x−3y−z<3−3<x−3y+z−3<x+3y−zx+y+3z<3x−y−3z<3−3<x−y+3z−3<x+y−3z