When in doubt, vectorise everything to do element-wise operations (unless you know you want to do matrix operations).
This will plot your graph:
h = .01;
x = 1:h:6;
y = (sqrt((x.^4)+1))./(2+sin(x)); % note that when you change the x vector, you need to recompute the y vect
figure(2)
plot(x,y)
Note the element-wise division (./) in your ‘y’ assignment.
