import math


def quadraticsolver(coeff):
    """
    Solves a quadratic equation
        :param coeff: list of all the coefficients of an equation
        :return: Roots of the equation
    """
    a,b,c,d=coeff
    c=c-d
    if a==0:
        return "Invalid equation"
    dis=b*b-4*a*c
    discrimi=math.sqrt(abs(dis))
    if dis > 0:
        r1=(-b + discrimi)/(2 * a)
        r2=(-b - discrimi)/(2 * a)
        return r1,r2
    elif dis == 0:
        return -b / (2*a)
    else:  
        return "No real root possible"