(*Definição de funções*)

F1[x_, y_] := 3  x + y^2

F2[x_, y_] := x^2 + 3  y - 1

j11[x_, y_] := D[F1[x, y], {x, 1}]

j12[x_, y_] := D[F1[x, y], {y, 1}]

j21[x_, y_] := D[F2[x, y], {x, 1}]

j22[x_, y_] := D[F2[x, y], {y, 1}]

J[x_, 
        y_] := {{j11[x, y], j12[x, y]}, {j21[x, y], j22[x, y]}}

x0 = 0. ;  y0 = 0. ; cont = 1; dif1 = 1; dif = 1; dx0 = 0; dy0 = 0; 
    While[dif > 0.0001  &&  cont < 10, Fn = {F1[x0, y0], F2[x0, y0]}; 
      Jn = J[x, y] /. {x -> x0, y -> y0}; {dx0, dy0} = 
        LinearSolve[Jn, -Fn]; 
x1 = x0 + dx0;  
      y1 = y0 + dy0; Print[" x1=", x1, "   y1=", y1]; 
      cont = cont + 1; dif = Sqrt[dx0^2 + dy0^2]; x0 = x1; y0 = y1; 
      Print["dif=", dif,  "   K=", dif/(dif1^2)]; 
      dif1 = dif]