Question: How to isolate a complex root?

restart:

lambda1:=(1/(K+2))*(S+sqrt(2*alpha*(K+2)+S^2));

lambda2:=(1/(K+2))*(S-sqrt(2*alpha*(K+2)+S^2));

where K>=0, S (-15, 15) and alpha (-15, 15). While plotting for small values of S and alpha, I get complex roots.

  • How we can avoid the complex roots?
  • Is it possible to impose a condition in plotting? 

    solve(lambda1=lambda2,S);

    solve(lambda1=lambda2,alpha);

    solve(lambda1=lambda2,K);

  • How to single out the range of S and alpha for which we have complex roots?

Thanks

 

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