If $$S=\left\{m \in R: x^2-2(1+3 m) x+7(3+2 m)=0\right.$$ has distinct roots}, then the number of elements in $$S$$ is

The sum of the real roots of the equation $$x^4-2 x^3+x-380=0$$ is

If one root of the cubic equation $$x^3+36=7 x^2$$ is double of another, then the number of negative roots are

If $$f(f(0))=0$$, where $$f(x)=x^2+a x+b, b \neq 0$$, then $$a+b=$$