Symbolic seems to have an error

Two typos in my original post corrected

[John D'Errico]

Then why did you feel the need to post it again? Just edit your original post. Anyway, it seems like everytime you don't understand a piece of code, you declare it to be a bug.

[Stephen Wilkerson]

We'll do you have an answer?

Answer 1

[Stephen Wilkerson]

Yes that's what I ended up doing.

Answer 2

[Stephen Wilkerson]

Now I'm unsure how to delete the second post?

Answer 3

[Paul]

The RHS of your differential equation should be 3*u.

In the frequency domain, Y(s) = H(s)*U(s). It looks like you're trying to get the step repsonse of your second order system, so U(s) = 1/s. You forgot to multiply by U(s) in your symbolic approach.

num = 3;
den = [1 2 5];

syms s
nums = poly2sym(num,s);
dens = poly2sym(conv(den,[1 0]),s);  % here!

ilaplace(nums/dens)
 
ans =
 
3/5 - (3*exp(-t)*(cos(2*t) + sin(2*t)/2))/5

[Stephen Wilkerson]

Thank you