How to solve system of non linear equation by iteration

clc

format long

x0 = input('Enter xo value');

y0= input('Enter yo value');

j=[1 1-4*y0; 2*x0 2*y0; 6*x0 -2*y0];

k=[(-4-(x0+y0-2*(y0)^2)); 8-((x0)^2+(y0)^2); 7.7-(3*(x0)^2-(y0)^2)];

dX=inv((j'*j))*j'*k;

x1=dX(1,1)+x0;

y1=dX(2,1)+y(i);

i need to use x1, y1 for the new iteration

thanks in advance