Finding gcd of polynomials with extra parameter in Maple

Question

My problem is that I have two functions in two variables, say $x$ and $y$. The functions are both polynomials in $x$, but sometimes $y$ appears in an exponent. What I want to do is find the gcd of these functions as if they are viewed as polynomials in $x$. However, when I use the gcd command it says it can not do it because the arguments must be polynomials. I have tried redefining the functions as just functions in $x$ (i.e. $h(x)$ $= f(x,y))$, but it still does not work. So is there anyway for me to get Maple to look at these functions as polynomials in $x$ and thus find the gcd? Or is there some other way I could do this?

Edit:

The polynomials I am working with a little complicated but here they are in general:

First, we define:

$$a(i,x,y) = (-1)^i(\binom{2y-1}{i-1}x^y+ \binom{2y-1}{i})$$

Now, our set of polynomials are:

$$f(i,x,y) = \binom{2y}{i-1} + \sum_{j=1}^{y}\binom{2y-j}{i-1}a(j,x,y) + \sum_{j=1}^{y-1}\binom{y-j}{i-1}a(y-j,x,y)x^j+\binom{0}{i-1}x^y$$

Where we use the convention $\binom{n}{k} =0$ if $k > n$.

What I am interested in determining is the gcd of $f(1,x,y)$ and $f(2,x,y)$. But Maple does not view them as polynomials as $y$ appears in the exponent, as stated above.

Answer 1

How are you passing the info?

From the help:

gcd(a, b, 'cofa', 'cofb')

The optional third argument cofa is assigned the cofactor a/gcd(a, b).

The optional fourth argument cofb is assigned the cofactor b/gcd(a, b).

Examples:

gcd(x^2-y^2,x^3-y^3,c,d);
                            -y+x
c;
                            x + y
d;
                         2          2
                        x  + x y + y