请教一下这个python代码哪里错误

定义求解一元二次方程的根的函数哪里错了，运行后一直提示定义函数语法错误

import math

def quadratic(a,b,c)
    if not isinstance(a,b,c,(int,float)):
       raise TypeError('bad operand type')
    d = b**2-4*a*c
    if d > 0:
       x1 = (-b+math.sqrt(d))/(2*a)
       x2 = (b+math.sqrt(d))/(2*a) 
    elif d = 0:
       x1 = -b/(2*a)
       x2 = x1
    else 
         return False    
x1,x2 = quadratic(2,3,1)
print(x1,x2)

修改如下，供参考：

import math

def quadratic(a,b,c):
    if isinstance((a,b,c),(int,int,int)):
       raise TypeError('bad operand type')
    d = b**2-4*a*c
    if d > 0:
        x1 = (-b+math.sqrt(d))/(2*a)
        x2 = (b+math.sqrt(d))/(2*a) 
    elif d == 0:
        x1 = -b/(2*a)
        x2 = x1
    else:
        return False
    return x1, x2

x1,x2 = quadratic(2,3,1)
print(x1,x2)