多项矩阵 ( a 11 a 12 … a 1 n a 21 a 22 … a 2 n ⋮ ⋮ ⋱ ⋮ a n 1 a n 2 … a n n ) \begin{pmatrix} a_{11} & a_{12} & \dots & a_{1n} \\ a_{21} & a_{22} & \dots & a_{2n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{n1} & a_{n2} & \dots & a_{nn} \\ \end{pmatrix} a11a21⋮an1a12a22⋮an2……⋱…a1na2n⋮ann
三角矩阵 ( a 11 a 12 … a 1 n a 22 ⋯ a 2 n ⋱ ⋮ a n n ) \begin{pmatrix} a_{11} & a_{12} & \dots & a_{1n} \\ & a_{22} & \cdots & a_{2n} \\ & & \ddots & \vdots \\ & & & a_{nn} \end{pmatrix} a11a12a22…⋯⋱a1na2n⋮ann