*make your list and work through it -- don't just guess and hope for the best!
Sometimes (even in math books) these things don't factor. So... when you are taking a test and you can't figure out if something will factor or not, what will you do?
b) mumble words that would shock your
c) work through your list and know, for sure,
that it really won't factor
I'd go with choice c if I were you.
Head on over to the next page for one more example!