[phpBB Debug] PHP Warning: in file [ROOT]/ext/alfredoramos/seometadata/event/listener.php on line 120: Undefined array key "description" Answer Happy • Show the set {(1, 0, 1, 0)T, (0, 1, 1
,1)T, (1, -1, 1, 0)T, (2, 1, 0,
1)T} is a basis for R4.
Show the set {(3, 1, -