Hyperplanes as Level Sets of Linear Functionals
In real vector spaces, Ω is a hyperplane iff Ω={x : f(x)=α} for some f≠0.
Let be a real vector space.
Proposition: A subset is a hyperplane if and only if there exist a nonzero linear functional and a scalar such that
Remarks
Context: One direction uses the decomposition of codimension-one subspaces (see codimension-one decomposition). The other direction uses that has codimension one (see codimension of kernels).