Theorem 1(Abel Theorem) If the power series is convergent at ,then for any that ,the power series absolutely converges at point ;if the power series is divergent at ,then for any that ,the power series diverges at point .

• 定理1(阿贝尔定理)如果级数当时收敛，则适当不等式的一切使这幂级数绝对收敛；反之，如果级数当时发散，则适合不等式的一切使这幂级数发散。