If you feel you're up to the task
and are falling short of time (and paper),
for a helpful shortcut you might ask.
Well listen closely and fight attention's taper.
Mental Substitution is the answer to your query,
but be warned such methods are no child's play.
Just remembering your "du" can prove rather weary.
Yet if you pull it off, powerful integrals you will slay.
To help you out, some pointers you might need:
Dealing with definite's requires a change in limits,
and restrictions to special trig subs you must heed.
Negative variables are also extremely important bits.
Take my advice and don't over to it.
I'll admit, it takes some serious wit,
but slow down occasionally and don't over think.
Because losing your train only takes a blink,
'n then you might find yourself in a separate institution!
Oh.. and while your there, don't forget to sub "u" back in!!!
