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# To really find a solution, Positively

During my research in Engineering, I came across this problem.

There is a complex valued function, with the domain as the imaginary axis.

$P(j\omega) = P_R(\omega^2)+j\omega P_I(\omega^2)$

I need to find the value of $$P(j\omega)$$, at the sequence of points where it is real and draw appropriate conclusions.

There are two scenarios here. (1) Both $$P_R(x)$$ and $$P_I(x)$$ are polynomials in $$x$$. (2) Not case 1.

For case 1 : As we are interested in values of $$P_R(\omega^2$$) at those $$\omega$$, where $$P_I(\omega^2)=0$$, it is obvious that we are interested ONLY in positive and real solutions to $$P_I(x)=0$$.

My question to the community is this.

• Are there any methods to find the real roots (or better positive real roots) of a polynomial, without actually finding all the roots?*

If there is no simpler solution, than finding all the roots; then the procedure which I envision would become more computationally complex than a conventional technique that is more than 80 years old.

If case 1 is worth pursuing, then case 2 could be an interesting extension.

Note by Janardhanan Sivaramakrishnan
10 months, 4 weeks ago