The uniqueness of limit cycle of quadratic system \((II)_{m=0}\)
In the paper the system \(x'=-y+\delta x+\ell x^ 2+y^ 2\), \(y'=x(1+ax)\), \(a<0\) is studied. Theorem: If, around the point (0,0), this system has limit cycles determined by saddle \((-1/a,y_ 1)\), \(y_ 1=(a+\sqrt{a^ 2-4(\ell -a\delta)})/2a,\) then it has at most one limit cycle.
scientific article; zbMATH DE number 4142494
scientific article