a) The gcd is the highest order polynomial that divides ( with no remainder) both f and g. It is unique.
and so x-1 is gcd
c) Since 1 and 3 zeroes you know that (x-1)(x-3) divides f.
So divide f by :
so the other two zeroes are the zeroes of , namely -1 and -2.
( I think this is correct - I forgot how that long division of polynomial is a pain )