\begin{pmatrix} 2 & 0 \\ 0 & -2 \end{pmatrix} ∑ n = 0 ∞ a n {\displaystyle \textstyle \sum _{n=0}^{\infty }a_{n}} a_n x = 0 {\displaystyle x=0} 조건수렴 무한급수
