Cancellation in equations

[Rem]

Hi,

I need help with the following (it is either not there or I couldn't find it
because I am still not quite awake!):

I have an equation that is being derived and I need to show some
cancellations during the evolution. Is there a way I can show the
cancellations, like a line segment (probably slope = 1, to be more specific)
drawn on a division?

I hope I was clear enough to be understood.. If not, I will drink more
coffee!

Thanks

Remzi