Using the relationship between
bilinear functionals and linear operators we obtain some theorems on the
extension of bilinear functionals. To extend bilinear functionals in Hilbert Spaces
a special constructional process is given which is a generalization of the
usual inner product. This allows the construction of bilinear functionals with
special properties. In particular it allows a generalization of the Lax-Milgram
Theorem. We also extend the Lax-Milgram Theorem to reflexive Banach
Spaces.