x'=F(x,y)
y'=G(x,y)
vriskw idiotimes tou pinaka tou susthmatos.|A-lI|=0
l1,2=m+iw
1.asumptwtika eystathes
  an m<0
2.eustathes an
  m=0
3.astathes an estw
  mia na exei m>0

thetw ta F(x)=x'(to iso tou) ,G(y)=y'(omoios)
x'=dF/dx(xo,yo)(x-xo)+dF/dy(xo,yo)(y-yo) +f(x,y)->0
y'=dG/dx(xo,yo)(x-xo)+dG/dy(xo,yo)(y-yo) +g(x,y)->0
upologizw dF/dx(xo,yo)....
antikathistw stis apopanw
thetw X=x-xo,Y=y-yo
X'=dF/dx(xo,yo)X+dF/dy(xy,yo)Y
Y'=dG/dx(xo,yo)X+dG/dy(xy,yo)Y
kai eksetaze thn efstatheia sto (0,0)

1.1 l1<l2<0 mh kanoniko komvo
1.2 l1=l2=0 kai duo gram aneks idiod. exoume komvo.
    an l1l2 suzugh exoume estia
2. l suzugh exoume kentro
3. l1>l2>0 astathi mi kanoniko komvo
   l1<0<l2 shmeio sellas
   l=l1=l2>0 astathi komvo
   l1l2 suzhgh astathi estia

