Factoring out expressions



Hello,

I've just started to use Maxima and I'm stumped at a this simple
problem. I have an expression of the form

                                       2            2
                   eq : t (b + a)  + t (y + x)

and I want to factor out "t". When I use the function factor or
factorsum t is correctly isolated
but (b+a)^2 and (y+x)^2 are expanded

                         2            2    2            2
(%o6)                t (y  + 2 x y + x  + b  + 2 a b + a )


When I use factorout I get the result that I'm looking for

                                              2                2
(%o5)                       t ((y + x)  + (b + a) )

but I have to pass y, x, b, and a as arguments to factorout

(%i5)                      factorout(eq, x, y, a, b)

which is not very practical when you have huge expressions full of
variables. Is there a similar function that takes
only the expression that I want to factor out as argument? I know how
to write a simple function to generate
the list with all the atoms and from that subtract the
variable/expression that I'm interested in but if there
is already a function that does what I want I'd rather use the
provided solution.

-- 
Daniel Cabrini Hauagge

email: daniel.hauagge at gmail.com
cel: +55 (19) 8194-8480