I don't know if this is the place where I can ask this. If not, please, tell me where.
This is a particular example of matrix I want to write in TeX commands. I was searching matrix stuff in "MathJax basic tutorial and quick reference" but, supossing I searched well, any of them makes a separation-lines between some blocks I want to distinguish. If it's possible, I also want the "big zero $0$ (a null matrix)" and the "big $I_{n-r}$ (identity matrix)" instead of the regular letter size.
I guess, something like
$$\left(\begin{array}{c|c} \begin{matrix}\frac{\partial f_1}{\partial x_1}&\cdots&\frac{\partial f_1}{\partial x_n}\\\vdots&&\vdots\\\frac{\partial f_n}{\partial x_1}&\cdots&\frac{\partial f_n}{\partial x_n}\end{matrix}&\begin{matrix}\frac{\partial f_1}{\partial x_1}&\cdots&\frac{\partial f_1}{\partial x_n}\\\vdots&&\vdots\\\frac{\partial f_n}{\partial x_1}&\cdots&\frac{\partial f_n}{\partial x_n}\end{matrix}\\\hline \huge{\mathbf O}&\huge{\mathbf I_{n-2}}\end{array}\right)$$
(right-click and select "Show Math As" > "TeX Commands" to see the code)
