function f = funcao_franke(x,y)

c = [3/4 3/4 1/2 -1/5];
a = [2 -1 7 4];
b = [2 -1 3 7];
u = [sqrt(2) 7/(sqrt(2)) sqrt(2) 1/(sqrt(2))];
v = [sqrt(2) 10/(sqrt(2)) sqrt(2) 1/(sqrt(2))];
R = 0.017;
x = x/R;
y = y/R;

soma = 0;
for i = 1:4
    soma = soma + ...
        c(i)*(exp(-0.5*((x-a(i))^2)/u(i)^2))*(exp(-0.5*((y-b(i))^2)/v(i)^2));
end
f = soma;