Simplify - specifying which variable is most important?

Questions
,
1

Hello,
Is it possible to get an expression simplified, but where I specify with variable is my main interest? For example, with the first screendump below, Simplify puts parameter a outside parentheses, but I would like to isolate all parts with a multiple of x and also for x^2, as x is my variable parameter, like in the second screendump below. Is there a way to do that?

1:

2683simplifybutnotwithrespecttox.jpg
2683simplifybutnotwithrespecttox.jpg763×134 23.8 KB

2:

simplifiedmyway.jpg

2

You can use Collect:

expr = (2 a d - 2 c^2 d + a^2 b E^(c x) + a^2 f - a c^2 f + a^2 e x - 
   a c^2 e x + a^2 d x^2 - a c^2 d x^2)/(
  a^2 (Sqrt[a] - c) (Sqrt[a] + c));
Collect[expr, x, Simplify]
Collect[expr, {x, E^(c x)}, Simplify]