def get_line_ABC_inter(line1, line2):
    """get line intersection point,
    line1: A1*x + B1*y + C1 = 0, [A1, B1, C1]
    line2: A2*x + B2*y + C2 = 0, [A2, B2, C2]
    inter = B1*A2 - A1*B2
    x = (C1*B2-B1*C2)/inter, y=(A1*C2-A2*C1)/inter
    """
    inter = line1[1]*line2[0] - line1[0]*line2[1]
    if inter != 0:
        x = (line1[2]*line2[1]-line1[1]*line2[2])/inter
        y = (line1[0]*line2[2] - line2[0]*line1[2])/inter
        return (x, y)
    return None