Theorem 9 (Rearrangement Theorem) The terms of an absolutely convergent series can be rearranged without affecting either the convergence or the sum of the series.

• 定理9(可交换性定理)绝对收敛级数经改变响的位置后构成的级数也收敛，且与原级数有相同的和(即绝对收敛级数具有可交换性)。