@Test
public void test2() {

    BackFilter f1=BackFilter.of(new double[]{1, -.7, .1});
    BackFilter f2=BackFilter.of(new double[]{1, .6, .5});
    BackFilter f=f1.times(f2);
    SymmetricFilter sf=SymmetricFilter.createFromFilter(f);
    SymmetricMullerNewtonSolver solver=new SymmetricMullerNewtonSolver();
    Polynomial P = Polynomial.copyOf(sf.getWeights());
    Complex[] roots = P.roots(solver);
      for (int i=0; i<roots.length; ++i){
          System.out.println(roots[i]);
      }
}