\[ \mathbf{x} = \left(\begin{array}(cccc)x_{11}&x_{22}&\idots&x_{1n}\\x_{11}&x_{22}&\idots&x_{1n}\\\vdots&\vdots&\ddots&\vdots\\x_{n1}&x_{n2}&\idots&x_{nn}\\\end{array}\right\]