Hi. Just some thoughts.
With multiple square roots, it brings to mind multiple solutions. Also,
note that it ae, or a<b, then you will be working with Complex numbers.
(Sqrt of negative numbers). Does this constraint hold? b<a<e? If C is the
opposite sign of D, you will have a sqrt of a negative number as well.
One additional method could be the Newton Equation. Goal Seek works great,
but can be limited in its accuracy. However, you can loop a few more times
in your own function.
This isn't fancy, and it doesn't have much error checking. Here's a simple
example using Mike's numbers...

Sub TestIt()
Debug.Print Fx(2, 3, 4, 5)
End Sub

Function Fx(b, c, d, e)
Dim K1
Dim K2
Dim a
Dim Num
Dim Den
Dim Last

K1 = b / 2
K2 = Sqr(c / d)
Last = 0
a = (b + e) / 2 'Middle
Do While Last < a
Last = a
Num = a + K1 - ((K2 * (e - a) ^ (3 / 2)) / Sqr(a - b))

Den = ((Sqr(e - a) * (2 * a - 3 * b + e) * K2) / _
(a - b) ^ (3 / 2) + 2) / 2

a = a - Num / Den
Debug.Print a

If a e Then a = e
If a < b Then a = b + 0.00001
Loop
End Function

Returns a = 2.68510380165928
which checks...

--
HTH :)
Dana DeLouis
Windows XP & Office 2003


"san2000" wrote in message
...
The equation has one unknown, but appear on both sides of the equation:

A+B/2 = SQRT(C/D) * [(E - A)^(3/2)] / [(A - B)^(1/2)]

THe only unknown that need to be solved is A. B, C, D, and E are known
variables. How to solve?