Only need to plot an auxiliar function with the numbers you want to plot in red markers example, (the whole numbers in x axis) try this
x = -3:0.01:5;
y = ((x+5).^2)./(4+3*x.^2);
plot(x,y)
hold on
X=-3:1:5;
Y=((X+5).^2)./(4+3*X.^2);
plot(X,Y,'r*')
grid on
This is how looks like:
