4th degree equations

12 views (last 30 days)
Asatur Khurshudyan
Asatur Khurshudyan on 18 Nov 2011
Hi, can anyone help me with this problem? We need the smallest positive real root of this equation
a*x^4+b*x^3+c*x^2+d*x+e=0,
where a>0, b<0, c>0, d<0 and e>0. As Descartes said, in that case this equation has at least 2 positive real roots.
Thank you for your attention.

Accepted Answer

Walter Roberson
Walter Roberson on 18 Nov 2011
r = roots([a,b,c,d,e]);
r(imag(r)~=0) = []; %remove complex
r(r <= 0) = []; %remove non-positive
min(r) %now it is the smallest positive real root
  5 Comments
Walter Roberson
Walter Roberson on 19 Nov 2011
I think I do not know enough polynomial theory to come up with a useful answer on this, sorry.
Asatur Khurshudyan
Asatur Khurshudyan on 20 Nov 2011
No, I mean with Matlab. If there exist exact method, than it must be done by mathlab, I suppose. All right, as you wish.

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!