Python实现一元二次方程的定义是：ax2 + bx + c = 0 请编写一个函数，返回一元二次方程的解。

<strong><span style="font-size:18px;">#杨鑫newlife
import math
def quadratic_equation(a, b, c):
    t = math.sqrt(pow(b, 2) - 4 * a * c)
    if(pow(b, 2) - 4 * a * c) > 0:
        return (-b + t) / (2 * a), (-b - t) / (2 * a)	
    elif (pow(b, 2) - 4 * a * c) == 0: 
        return (-b + t) / (2 * a)
    else:
	    return None
print quadratic_equation(2, 3, 0)
print quadratic_equation(1, -6, 5)</span></strong>