solving system of nonlinear equations

Hi, I have a problem with my homework. Definition: The nonlinear system

f(x1,x2)=x(1)^2 - x(2)^2 + 2*(x(2));

f(x1,x2)=2*x(1) + x(2) - 6;

has two solutions (0.625204094,2.179355825) and (2.109511920,-1.334532188). Use Runge-Kutta method of order four with N=1 to approximate the solutions where x(0)=(0,0), x(0)=(1,1) and x(0)=(3,-2).

So, I wrote it in Jacobian matrix and then I tried to solve it with RK4 method in one step. But I do not get even close to the solution.

Could you help me with suggestions, how to solve this problem or even write a code? I do not know, where I did a mistake. Thanks and have a great day ;)