n=50;a=0;b=3;
x=linspace(a,b,n);
e1=exp(-x.^2);
e2=(x.^2).*exp(-x.^2);
e3=x.*exp(-x.^2);
e4=exp(-x);
hold on;plot(x,e1,'linewidth',1);plot(x,e2,'linewidth',2);plot(x,e3,'linewidth',3);plot(x,e4,'linewidth',4);legend('y=e^-^x^(^2^)','y=x^2*e^-^x^(^2^)','y=x*e^-^x^(^2^)','y=e^-^x')
hold off