An approximate solution of (18) can be expressed in the form
where 
and 
are
respectively the Fredholm determinant and the Fredholm first minor of the
kernel 
and are expressible as power series in b
[121]:
The coefficients 
can be computed by using the following relations
[82]
Substituting 
from (19)
and
comparing the result with (8) we identify the kernel of an
equivalent feed-forward operator 
The application of parametric mapping leads to
where 
, being 
the Jacobian of the
transformation 
.
