Mallorca win boosts survival hopes
With two rounds left, 19th-place Mallorca is three points behind 17th-place Deportivo La Coruna but with an inferior goal difference.
Mallorca striker Tomer Hemed scored in the 21st minute from close to the penalty spot after goalkeeper Adrian San Miguel saved Victor Casadesus Castano's initial shot.
Betis stayed seventh in the standings on 52 points.
Mallorca plays Atletico Madrid and Valladolid before the season ends.
Barcelona has already clinched the league title and can match Real Madrid's 2012 record haul of 100 points by winning its last two matches.