Hi, I am trying to produce the most abbreviated expression of the formulas inside the resulting matrix

of the following code:

as = Variance[Table[u[i, t] - u[i, t - 1], {t, 1, 3}, {i, 1, 2}]];

MatrixForm[Simplify[as, Element[u[_, _], Reals]]];

cv = Covariance[Table[u[i, t] - u[i, t - 1], {t, 1, 3}, {i, 1, 2}]];

MatrixForm[Simplify[cv, Element[u[_, _], Reals]]];

MatrixForm[

D[Simplify[((as + 2*cv)^(1/2))*F, Element[u[_, _], Reals]], u[1, 2]]]

--> I am trying to abbreviate the result into the most simplfied expression of the resulting matrix only except the diagonal elements.

If so, how can I do this work?

Besides, when I try the different partial derivative formula like:

MatrixForm[

D[Simplify[((as + 2*cv)^(1/2))*F, Element[u[_, _], Reals]], u[1, 1]]]

The result of the position (1,1) of the resulting matrix is:

6^(1/2)* F *Abs'*[u[1, 0] - 2 u[1, 1] + u[1, 2]]

How can I fix this " Abs' " into the real number format that I can use practically?

I would greatly appreciate if I could get any helps on this problem.

Thank you very much!