I'm not sure why you need an iterative function. A little algebra gives

C4*E4^2 + E4 - A = 0

E4 = (-1 ± SQRT(1^2 - 4*C4*(-A)) ) / (2*C4)

So one solution for E4 will be

E4 = (-1 + SQRT(1+4*$C$4*A))/(2*$C$4)

and the other will be

E4 = (-1 - SQRT(1+4*$C$4*A))/(2*$C$4)



In article ,
Eddy VG wrote:

A mathematical formulae of the type A = E4*(1+(C4*E4)) in which C4 is a
fixed value and A has values listed in a row in an excel-worksheet.
The different values of E4 has to be determined as a function of A.
Is there a iteration function available and how should it be
specified.
All advice is appreciated!