F=@(x) [-20*x(1)^2 +1 -2*x(1)^3 + 4*x(2)^3, -10*x(2) 51 + 2*x(1)^3 -3*x(2)^2];

ezplot('-20*x^2 +1 -2*x^3 + 4*y^3')
hold on
grid on
m=ezplot ('-10*y +5 +2*x^3 -3*y^2')
set (m,'color','r')
hold off

lahend1=fsolve(F, [-0.26, 0.45])
kontroll1= F(lahend1)

lahend2=fsolve(F, [0.26, 0.45])
kontroll2= F(lahend2)

lahend3=fsolve(F, [3.72, 4.56])
kontroll3= F(lahend3)