Sequences and series calculator

Sequences_calc.py

def Quadratic():
    option = int(input("Options: 1) Enter formula 2) Enter three terms"))
    if option == 2:
        terms = [None, None, None, None]
        for i in range(1,4):
            terms[i] = float(input(str("Enter term " + str(i) + ": ")))
        diff1 = terms[2] - terms[1]
        diff2 = terms[3] - terms[2]
        quadiff = diff2 - diff1
        a = quadiff / 2
        quadiff2 = [None, None, None, None]
        for i in range(1,4):
            quadiff2[i] = terms[i] - (a*(i**2))
        nthdiff = quadiff2[2] - quadiff2[1]
        zeroterm = quadiff2[1] - nthdiff
    elif option == 1:
        print("an^2 + bn + c")
        a = float(input("Enter a: "))
        nthdiff = float(input("Enter b: "))
        zeroterm = float(input("Enter c: "))
    else:
        print("Error")
        exit()
    nthTerm = str(str(a) + "n^2 " + "+ " + str(nthdiff) + "n" + " + " + str(zeroterm))
    print(nthTerm)
    const1 = a
    const2 = nthdiff
    const3 = zeroterm
    option = int(input("Options: 1) Show 10 terms 2) Calculate nth term 3) Find term number "))
    if option == 1:
        for i in range(1,11):
            print("Term " + str(i) + ": " + str((const1 * (i ** 2)) + (const2 * i) + (const3)))
    elif option == 2:
        nth = int(input("n:"))
        answer = (const1 * (nth ** 2)) + (const2 * nth) + (const3)
        print(answer)
    elif option == 3:
        value = float(input("Term value: "))
        nth = 0
        answer = None
        while answer != value:
            nth += 1
            answer = (const1 * (nth ** 2)) + (const2 * nth) + (const3)
        if answer > value:
            print("Error")
        elif answer == value:
            print("n: " + str(nth))
        else:
            print("???")
def Geometric():
    option = int(input("1) Enter Formula 2) Enter first two terms : "))
    if option == 1:
        a = float(input("Enter first number of sequence: "))
        r = float(input("Enter ratio: "))
    elif option == 2:
        a = float(input("Enter first number of sequence: "))
        a2 = float(input("Enter second number of sequence: "))
        r = a2/a
    else:
        print("Error")
        exit()
    option = int(input("1) Show 10 terms 2) Calculate nth term 3) Find term number : "))
    print("Formula: " + str(a) + "*" + str(r) + "^(n-1)")
    if option == 1:
        for n in range(1,11):
            value = a * (r**(n-1))
            print("Term " + str(n) + ": " + str(value))
    elif option == 2:
        n = int(input("Enter term number: "))
        value = a * (r**(n-1))
    elif option == 3:
        userVal = float(input("Enter term value: "))
        n = 0
        value = None
        while value != userVal and value < userVal:
            n += 1
            value = a * (r**(n-1))
        if value == userVal:
            print("Nth term: " + str(n))
        else:
            print("Error")

option = int(input("1) Quadratic 2) Geometric : "))
if option == 1:
    Quadratic()
elif option == 2:
    Geometric()
else:
    print("Error")