reserve x for set,
  p,q,r,s,t,u for ExtReal,
  g for Real,
  a for Element of ExtREAL;

theorem
  for r being Real holds [.r,+infty.[ = {r} \/ ].r,+infty.[
proof
  let r be Real;
  r in REAL by XREAL_0:def 1;
  hence thesis by Th131,XXREAL_0:9;
end;
