用python求一元二次方程的根

你好！

math
math, sqrt, b, 2, a, c
-b-math.sqrt(b**2-4*a*c)
False
flag
flag, ==
True
a, 'a:'
b, 'b:'
c, 'c:'
a, b, c
a,b,c
r1, r2
"The roots are complex"