Simplify gives different results with and without a=1

[Neitrino]

Help urgently needed in Mathematica Simplify

Dear All,

I have a very longe expression (see file attached ) of variables x, a, Lambda... etc,
when I apply "Simplify" I am left only with very short expression
ONLY with variable Lambda.

But if in the initial expression I declare "a" variable as equal to one (a = 1) and afterwrds try to do simplification it gives me ZERO!.

So why this happen .. If the first "Simplify" tells me that the expression is dependent only on Lambda why "a" variable affects the result ...?

Pls heelp... what I do wrong...
George

 

[Hepth]

I assume there's some zeroes. The first answer is correct, as you can see if you do :
Limit[fx[a],a->1]
its the a independent solution. The second part (where it is 0) is most likely due to these divide by zeroes, where mathematica cannot correctly simplify it.