The equation
represents an -dimensional hypersphere as a quadratic hypersurface in an -dimensional real projective space , where are homogeneous coordinates in . Then the group of projective transformations which leave invariant is called the Möbius group.
More things to try:
Weisstein, Eric W. "Möbius Group." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/MoebiusGroup.html
-dimensional
hypersphere 
as a quadratic hypersurface in an 
-dimensional real projective space 
, where 
are homogeneous coordinates in 
. Then the group 
of projective transformations which leave 
invariant is called the Möbius group.
