how do i plot a complicated function

i tried to plot a function but it only produced an empty image

clc;

clear all;

alpha = 2;

gamma = 3;

k1 = 0.5;

k2 = 0.15;

eta = @(x,y)(sqrt((x*k1+gamma*(1-y)-alpha)^2-4*x.*(gamma*k2*(1-y)-alpha*k1))-(x*k1+gamma*(1-y)-alpha))/(2*x);

F = @(x,y)alpha-2*x.*eta-(k1*(alpha-x.*eta))/(x+k1)-(1-y);

fimplicit(F,[-20 20 -20 20])

Answer 1

[Stephan]

alpha = 2;
gamma = 3;
k1 = 0.5;
k2 = 0.15;

syms eta(x,y) Eta

eta(x,y) = (sqrt((x*k1+gamma*(1-y)-alpha)^2-4*x.*(gamma*k2*(1-y)-alpha*k1))-(x*k1+gamma*(1-y)-alpha))/(2*x);
F(x,y) =  alpha-2*x.*Eta-(k1*(alpha-x.*Eta))/(x+k1)-(1-y);
fun = subs(F,Eta,eta)

fun(x, y) = 

fimplicit(fun,[-2 1 -50 20])