Algebraic manipulation

[BruceH]

I don't know of a way to use a specific factor.

Alternatives:

• Use the factors() command to get a list of the factors. You can then inspect the list to see if the one you are expecting is present.
• Or, do a test divide by your factor, e.g. simplify((4*x-12)/(x-3))? If your divisor remains unchanged then it isn't a factor.