How to use X as a int()

I'm starting with Python and I've made a code that calculates Newton's Binomial Theorem (for example: (2+9)⁹(= [256, 9216, 145152, 1306368, 7348320, 26453952, 59521392, 76527504, 43046721]) if I input the elevation, the first term and the second term. The problem is that I have no clue in how I could make it to be able to calculate (X+9)⁹.With this i mean that i have no clue of how i could input a x and tell the program to do opperations as if it was a int(), for example (x+3)³ = [x², 6x, 9]. I'm asking if there is any way to do it.

This is the code:

from math import *

def combinacio(n,k):
    return int(factorial(n)/(factorial(k)*factorial(n-k)))

potencia = int(input("Inserta la potencia de el binomi: "))
yo = int(input("Inserta el primer terme: "))
xo =  int(input("Inserta el segon terme: "))
fila_preguntada = potencia

def pascal(files):
    resultat = []
    #aquí es on es la llista on es guarda el resultat
    for count in range(files):
        #conta les integres de 0 fins a files-1 i per cada loop dona el valor de count, ex:nº files = 3, fa un loop pel num 0, i pel 1 i el 2
        fila = []
        #una altra llista
        for element in range(count+1):
        #conta les integres de 0 fins a count+1 i ho guarda com a valor de element, ex: files = 3, 1r loop on count és 0, aqui li suma 1, llavors li dona que element és 0, pel 2n loop, element es 1, 3r loop 2
            fila.append(combinacio(count,element))
            #li afageix a la fila la combinacio de count i element, ex: count= 0, element = 0, count = 1, element = 1,count= 2, element = 2, llavors fila seria [1,2,1]
    resultat.append(fila)
    #afageix el resultat de fila a resultat
    return resultat

def agafar_la_llista():
    for fila in pascal(fila_preguntada):
    #busca la variable fila fent la variable pascal amb l'argument fila_preguntada.
        return fila

def fer_la_potencia_de_X():
    llista_x = []
    for x in range(potencia):
        xp = xo**x
        llista_x.append(xp)
    return llista_x

def fer_la_potencia_de_Y():
    llista_y = []
    for y in range((potencia-1),-1,-1 ):
        yp = yo**y
        llista_y.append(yp)
    return llista_y

def resposta_final():
    pascal = agafar_la_llista()
    X = fer_la_potencia_de_X()
    Y = fer_la_potencia_de_Y()
    resultat_final = []
    for m in range(potencia):
        k = pascal[m] * X[m] * Y[m]
        resultat_final.append(k)
    print (resultat_final)

resposta_final()