Question: numeric manipulation in maple

There was mention to have simplify=false in Maple to stop it from it's automatic manipulation which would otherwise be considered obvious but not necessarily wanted. 

The idea brings up numeric manipulation. 

For example how do I force maple to factor out (1/3) from this :

a:= (1/3)*x^2 + (1/6)*x - (1/12)

to to show this

(1/3) * ( x^2 + x/2 - 1/4 )

Things brings up another question, the collect command won't work to factor out numerics so we could instead substitute the value 1/3 to a variable say k.  But you can't equate 1/3:=k so how could we do it?

We could multiply a by k and the inverse of the value we want to substitute to substitute our value k for 1/3

a*3*k

then we need to
simplify(%)

then we can
collect(%,k)

we know k is 1/3 so at least it's in the form we wanted. 

This brings another question which has been asked before, how do I move the k out front? 

But first subing 1/3 back into k just brings us right back to square one (This is where simplify=false would come in handy)

Any thoughts on all of my questions?