x = (-10.0 : 0.5 : 25.0)';
y1 = normpdf(x, 3, sqrt(6));    
y2 = normpdf(x, 10, sqrt(5));
plot(x, y1, '-.r', 'linewidth', 2);
hold on
plot(x, y2, '--g', 'linewidth', 2);
plot(x,(y1+y2)/2, '-b', 'linewidth', 2);
legend('N(3,6)', 'N(10,5)', '0.5*N(3,6) + 0.5*N(10,5)')
hold off