爬虫求接，需要大能帮助，显示格式错误，不明白什么情况

a,b,c=map(float,input().split())
f=b2-4ac
if a==0 and b==0 and c==0:
print("Zero Equation")
elif a==0 and b==0:
print("Not An Equation")
elif a==0:
e=-c/b
print("{:.2f}".format(e))
elif f==0:
e=(-b+f0.5)/(2a)
print("{:.2f}".format(e))
elif f>0:
s=(-b+f**0.5)/(2a)
d=(-b-f*0.5)/(2a)
if s>d:
s,d=d,s
print("{:.2f} {:.2f}".format(d,s))
elif f<0:
r=(-f)/(2a)
e=-b/(2a)
print("{:.2f}+{:.2f}i".format(e,r))
print("{:.2f}-{:.2f}i".format(e,r))