\[\begin{bmatrix}u_{11}&u_{12}&\cdots&u_{1n}&y_{1}\\
0&u_{22}&\cdots&u_{2n}&y_{2}\\
\vdots&\ddots&\ddots&\vdots&\vdots\\
0&\cdots&0&u_{nn}&y_{n}\end{bmatrix}.\]