want to get only all positive real roots

Compute all positive real roots of x^4 + 2*x^3 − 7*x^2 + 3 = 0.

I want to discard all the imaginary ones and keep only the positive real root only

Can someone please guide me on that???

[Steven Lord]

Show us what you've written so far and we may be able to suggest how to modify your code to return the positive real roots.

Answer 1

[Raj]

Use this:

p=[1 2 -7 0 3] % Your Polynomial equation coefficients matrix
A=roots(p) % All roots of equation
B=A(A>=0) % Only positive real roots of equation

This will be a useful read.

[Walter Roberson]

That does not test the imaginary components.

B = A(real(A) >= 0 & imag(A) == 0)

[Raj]

Agreed. No imaginary roots in this equation though.

[Walter Roberson]

Looks like this particular equation has only real roots, two negative and two postive.

[Dokeun Hwang]

The answer above gives all the real parts in the roots

So, it should be corrected as below

B=A(real(A)>0&imag(A)==0);

ref: https://kr.mathworks.com/matlabcentral/answers/89612-how-to-select-real-positive-number